diff --git a/.gitignore b/.gitignore
index df93547..e1033af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,7 @@ lib
 include
 man
 parts
+*.egg-info/
 
 __pycache__
 .*
@@ -13,3 +14,7 @@ __pycache__
 *.pyc
 *.pyo
 *.so
+
+coverage.xml
+htmlcov/
+eggs/
diff --git a/.travis.yml b/.travis.yml
index dce0257..72e76ff 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,10 +1,29 @@
 language: python
+sudo: false
 python:
     - 2.7
+    - 3.4
+    - 3.5
+    - 3.6
+
 install:
-    - python bootstrap.py
-    - bin/buildout
+    - pip install six==1.10.0 # force here to avoid conflict with zc.recipe.testrunner
+    - pip install -U setuptools==33.1.1
+    - pip install coveralls coverage
+    - pip install zc.buildout
+    - buildout bootstrap
+    - buildout
+
 script:
-    - bin/test -v1
+    - coverage run bin/test -v1
+after_success:
+    - coverage combine
+    - coveralls
+
 notifications:
     email: false
+
+cache:
+  pip: true
+  directories:
+    - eggs/
diff --git a/CHANGES.rst b/CHANGES.rst
index 538d3bb..36283a6 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -6,6 +6,12 @@ Changelog
 
 - Zope trunk compatibility for product init.
 
+- Fix _findModificationTime for ZODB 5
+  [davisagli]
+
+- Add Support for Python 3
+  [rudaporto, pbauer, icemac, davisagli]
+
 1.1.3 - 2010-10-02
 ------------------
 
diff --git a/bootstrap.py b/bootstrap.py
new file mode 100644
index 0000000..a629566
--- /dev/null
+++ b/bootstrap.py
@@ -0,0 +1,189 @@
+##############################################################################
+#
+# Copyright (c) 2006 Zope Foundation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""Bootstrap a buildout-based project
+
+Simply run this script in a directory containing a buildout.cfg.
+The script accepts buildout command-line options, so you can
+use the -c option to specify an alternate configuration file.
+"""
+
+import os
+import shutil
+import sys
+import tempfile
+
+from optparse import OptionParser
+
+tmpeggs = tempfile.mkdtemp()
+
+usage = '''\
+[DESIRED PYTHON FOR BUILDOUT] bootstrap.py [options]
+
+Bootstraps a buildout-based project.
+
+Simply run this script in a directory containing a buildout.cfg, using the
+Python that you want bin/buildout to use.
+
+Note that by using --find-links to point to local resources, you can keep
+this script from going over the network.
+'''
+
+parser = OptionParser(usage=usage)
+parser.add_option("-v", "--version", help="use a specific zc.buildout version")
+
+parser.add_option("-t", "--accept-buildout-test-releases",
+                  dest='accept_buildout_test_releases',
+                  action="store_true", default=False,
+                  help=("Normally, if you do not specify a --version, the "
+                        "bootstrap script and buildout gets the newest "
+                        "*final* versions of zc.buildout and its recipes and "
+                        "extensions for you.  If you use this flag, "
+                        "bootstrap and buildout will get the newest releases "
+                        "even if they are alphas or betas."))
+parser.add_option("-c", "--config-file",
+                  help=("Specify the path to the buildout configuration "
+                        "file to be used."))
+parser.add_option("-f", "--find-links",
+                  help=("Specify a URL to search for buildout releases"))
+parser.add_option("--allow-site-packages",
+                  action="store_true", default=False,
+                  help=("Let bootstrap.py use existing site packages"))
+parser.add_option("--setuptools-version",
+                  help="use a specific setuptools version")
+
+
+options, args = parser.parse_args()
+
+######################################################################
+# load/install setuptools
+
+try:
+    if options.allow_site_packages:
+        import setuptools
+        import pkg_resources
+    from urllib.request import urlopen
+except ImportError:
+    from urllib2 import urlopen
+
+ez = {}
+exec(urlopen('https://bootstrap.pypa.io/ez_setup.py').read(), ez)
+
+if not options.allow_site_packages:
+    # ez_setup imports site, which adds site packages
+    # this will remove them from the path to ensure that incompatible versions
+    # of setuptools are not in the path
+    import site
+    # inside a virtualenv, there is no 'getsitepackages'.
+    # We can't remove these reliably
+    if hasattr(site, 'getsitepackages'):
+        for sitepackage_path in site.getsitepackages():
+            sys.path[:] = [x for x in sys.path if sitepackage_path not in x]
+
+setup_args = dict(to_dir=tmpeggs, download_delay=0)
+
+if options.setuptools_version is not None:
+    setup_args['version'] = options.setuptools_version
+
+ez['use_setuptools'](**setup_args)
+import setuptools
+import pkg_resources
+
+# This does not (always?) update the default working set.  We will
+# do it.
+for path in sys.path:
+    if path not in pkg_resources.working_set.entries:
+        pkg_resources.working_set.add_entry(path)
+
+######################################################################
+# Install buildout
+
+ws = pkg_resources.working_set
+
+cmd = [sys.executable, '-c',
+       'from setuptools.command.easy_install import main; main()',
+       '-mZqNxd', tmpeggs]
+
+find_links = os.environ.get(
+    'bootstrap-testing-find-links',
+    options.find_links or
+    ('http://downloads.buildout.org/'
+     if options.accept_buildout_test_releases else None)
+    )
+if find_links:
+    cmd.extend(['-f', find_links])
+
+setuptools_path = ws.find(
+    pkg_resources.Requirement.parse('setuptools')).location
+
+requirement = 'zc.buildout'
+version = options.version
+if version is None and not options.accept_buildout_test_releases:
+    # Figure out the most recent final version of zc.buildout.
+    import setuptools.package_index
+    _final_parts = '*final-', '*final'
+
+    def _final_version(parsed_version):
+        try:
+            return not parsed_version.is_prerelease
+        except AttributeError:
+            # Older setuptools
+            for part in parsed_version:
+                if (part[:1] == '*') and (part not in _final_parts):
+                    return False
+            return True
+
+    index = setuptools.package_index.PackageIndex(
+        search_path=[setuptools_path])
+    if find_links:
+        index.add_find_links((find_links,))
+    req = pkg_resources.Requirement.parse(requirement)
+    if index.obtain(req) is not None:
+        best = []
+        bestv = None
+        for dist in index[req.project_name]:
+            distv = dist.parsed_version
+            if _final_version(distv):
+                if bestv is None or distv > bestv:
+                    best = [dist]
+                    bestv = distv
+                elif distv == bestv:
+                    best.append(dist)
+        if best:
+            best.sort()
+            version = best[-1].version
+if version:
+    requirement = '=='.join((requirement, version))
+cmd.append(requirement)
+
+import subprocess
+if subprocess.call(cmd, env=dict(os.environ, PYTHONPATH=setuptools_path)) != 0:
+    raise Exception(
+        "Failed to execute command:\n%s" % repr(cmd)[1:-1])
+
+######################################################################
+# Import and run buildout
+
+ws.add_entry(tmpeggs)
+ws.require(requirement)
+import zc.buildout.buildout
+
+if not [a for a in args if '=' not in a]:
+    args.append('bootstrap')
+
+# if -c was provided, we push it back into args for buildout' main function
+if options.config_file is not None:
+    args[0:0] = ['-c', options.config_file]
+
+zc.buildout.buildout.main(args)
+shutil.rmtree(tmpeggs)
diff --git a/buildout.cfg b/buildout.cfg
new file mode 100644
index 0000000..9a8a35b
--- /dev/null
+++ b/buildout.cfg
@@ -0,0 +1,22 @@
+[buildout]
+extends =
+    https://raw.githubusercontent.com/zopefoundation/Zope/master/versions.cfg
+    https://raw.githubusercontent.com/zopefoundation/Zope/master/sources.cfg
+develop = .
+parts = interpreter test coverage
+
+[interpreter]
+recipe = zc.recipe.egg
+interpreter = python
+eggs =
+    AccessControl
+    tox
+
+[test]
+recipe = zc.recipe.testrunner
+eggs = Products.ZopeVersionControl
+
+[coverage]
+recipe = zc.recipe.testrunner
+eggs = Products.ZopeVersionControl
+defaults = ['--coverage', '../../coverage', '-v', '--auto-progress']
diff --git a/setup.py b/setup.py
index 8274357..f70d0e3 100755
--- a/setup.py
+++ b/setup.py
@@ -12,6 +12,10 @@
         'Framework :: Zope2',
         'Programming Language :: Python',
         'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 3.4',
+        'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
     ],
     license='ZPL',
     author='Zope Foundation and Contributors',
@@ -28,7 +32,8 @@
         'Acquisition',
         'DateTime',
         'transaction',
-        'ZODB3',
+        'six',
+        'ZODB',
         'Zope2',
     ],
 )
diff --git a/src/Products/ZopeVersionControl/EventLog.py b/src/Products/ZopeVersionControl/EventLog.py
index ca80bb6..ba1216c 100644
--- a/src/Products/ZopeVersionControl/EventLog.py
+++ b/src/Products/ZopeVersionControl/EventLog.py
@@ -11,11 +11,12 @@
 #
 ##############################################################################
 
+from .Utility import _findUserId
 from App.class_init import default__class_init__ as InitializeClass
-from Persistence import Persistent
 from AccessControl import ClassSecurityInfo
 from BTrees.IOBTree import IOBTree
-from Utility import _findUserId
+from Persistence import Persistent
+
 import time
 
 MAX32 = int(2**31 - 1)
diff --git a/src/Products/ZopeVersionControl/Repository.py b/src/Products/ZopeVersionControl/Repository.py
index bb8bfc3..b5a93dd 100644
--- a/src/Products/ZopeVersionControl/Repository.py
+++ b/src/Products/ZopeVersionControl/Repository.py
@@ -11,25 +11,22 @@
 #
 ##############################################################################
 
-__version__='$Revision: 1.14 $'[11:-2]
-
-import time
-from random import randint
-
+from . import Utility
+from .EventLog import LogEntry
+from .nonversioned import getNonVersionedData, restoreNonVersionedData
+from .Utility import isAVersionableResource, VersionControlError, VersionInfo
+from .Utility import use_vc_permission, _findPath
+from .ZopeVersionHistory import ZopeVersionHistory
+from AccessControl import ClassSecurityInfo
 from Acquisition import Implicit, aq_parent, aq_inner
-from ZopeVersionHistory import ZopeVersionHistory
 from App.class_init import default__class_init__ as InitializeClass
-from Persistence import Persistent
-from AccessControl import ClassSecurityInfo
-from Utility import use_vc_permission, _findPath
-from Utility import isAVersionableResource, VersionControlError, VersionInfo
-from DateTime.DateTime import DateTime
-from BTrees.OOBTree import OOBTree
 from BTrees.OIBTree import OIBTree
+from BTrees.OOBTree import OOBTree
+from DateTime.DateTime import DateTime
+from Persistence import Persistent
+from random import randint
 
-from EventLog import LogEntry
-import Utility
-from nonversioned import getNonVersionedData, restoreNonVersionedData
+import time
 
 
 class Repository(Implicit, Persistent):
@@ -55,7 +52,7 @@ def createVersionHistory(self, object):
         # the version or version history yet have a _p_jar, which causes
         # copy operations to fail. To work around that, we share our _p_jar.
         history_id = None
-        while history_id is None or self._histories.has_key(history_id):
+        while history_id is None or history_id in self._histories:
             history_id = str(randint(1, 9999999999))
         history = ZopeVersionHistory(history_id, object)
         self._histories[history_id] = history
@@ -81,8 +78,8 @@ def replaceState(self, obj, new_state):
                 "The class of the versioned object has changed. %s != %s"
                 % (repr(obj.__class__, new_state.__class__)))
         obj._p_changed = 1
-        for key in obj.__dict__.keys():
-            if not new_state.__dict__.has_key(key):
+        for key in list(obj.__dict__.keys()):
+            if not key in new_state.__dict__:
                 del obj.__dict__[key]
         for key, value in new_state.__dict__.items():
             obj.__dict__[key] = value
@@ -328,23 +325,24 @@ def updateResource(self, object, selector=None):
             # If the selector is non-null, we find the version specified
             # and update the sticky tag. Later we'll check the version we
             # found and decide whether we really need to update the object.
-            if history.hasVersionId(selector):
+            if type(selector) is str and history.hasVersionId(selector):
                 version = history.getVersionById(selector)
                 sticky = ('V', selector)
 
-            elif self._labels.has_key(selector):
+            elif type(selector) is str and selector in self._labels:
                 version = history.getVersionByLabel(selector)
                 sticky = ('L', selector)
 
-            elif self._branches.has_key(selector):
+            elif type(selector) is str and selector in self._branches:
                 version = history.getLatestVersion(selector)
                 if selector == 'mainline':
                     sticky = None
                 else:
                     sticky = ('B', selector)
             else:
-                try:    date = DateTime(selector)
-                except:
+                try:
+                    date = DateTime(selector)
+                except Exception:
                     raise VersionControlError(
                         'Invalid version selector: %s' % selector
                         )
@@ -386,11 +384,11 @@ def labelResource(self, object, label, force=0):
                 )
 
         # Make sure that labels and branch ids do not collide.
-        if self._branches.has_key(label) or label == 'mainline':
+        if label in self._branches or label == 'mainline':
             raise VersionControlError(
                 'The label value given is already in use as an activity id.'
                 )
-        if not self._labels.has_key(label):
+        if not label in self._labels:
             self._labels[label] = 1
 
         history = self.getVersionHistory(info.history_id)
@@ -412,17 +410,17 @@ def makeActivity(self, object, branch_id):
         branch_id = branch_id or None
 
         # Make sure that activity ids and labels do not collide.
-        if self._labels.has_key(branch_id) or branch_id == 'mainline':
+        if branch_id in self._labels or branch_id == 'mainline':
             raise VersionControlError(
                 'The value given is already in use as a version label.'
                 )
 
-        if not self._branches.has_key(branch_id):
+        if not branch_id in self._branches:
             self._branches[branch_id] = 1
 
         history = self.getVersionHistory(info.history_id)
 
-        if history._branches.has_key(branch_id):
+        if branch_id in history._branches:
             raise VersionControlError(
                 'The resource is already associated with the given activity.'
                 )
@@ -442,11 +440,11 @@ def getVersionOfResource(self, history_id, selector):
                 version = history.getVersionById(selector)
                 sticky = ('V', selector)
 
-            elif self._labels.has_key(selector):
+            elif selector in self._labels:
                 version = history.getVersionByLabel(selector)
                 sticky = ('L', selector)
 
-            elif self._branches.has_key(selector):
+            elif selector in self._branches:
                 version = history.getLatestVersion(selector)
                 sticky = ('B', selector)
             else:
diff --git a/src/Products/ZopeVersionControl/Utility.py b/src/Products/ZopeVersionControl/Utility.py
index 08868bd..83d2196 100644
--- a/src/Products/ZopeVersionControl/Utility.py
+++ b/src/Products/ZopeVersionControl/Utility.py
@@ -70,7 +70,7 @@ def clone(self, clear_sticky=0):
         for name, value in self.__dict__.items():
             dict[name] = value
         if clear_sticky:
-            if dict.has_key('sticky'):
+            if 'sticky' in dict:
                 del dict['sticky']
         info.user_id = _findUserId()
         info.timestamp = time.time()
@@ -128,35 +128,31 @@ def _findModificationTime(object):
     latest = mtime
     conn = object._p_jar
     load = conn._storage.load
-    try:
-        version = conn._version
-    except AttributeError:
-        # ZODB 3.9+ compatibility
-        version = None
     refs = referencesf
 
-    oids=[object._p_oid]
-    done_oids={}
-    done=done_oids.has_key
+    oids = [object._p_oid]
+    done_oids = set()
+    done = done_oids.__contains__
     first = 1
 
     while oids:
-        oid=oids[0]
+        oid = oids[0]
         del oids[0]
         if done(oid):
             continue
-        done_oids[oid]=1
-        try: p, serial = load(oid, version)
-        except: pass # invalid reference!
+        done_oids.add(oid)
+        try:
+            p, serial = load(oid)
+        except Exception:
+            pass  # invalid reference!
         else:
             if first is not None:
                 first = None
             else:
-                if p.find('U\x0b__vc_info__') == -1:
+                if p.find(b'U\x0b__vc_info__') == -1:
                     mtime = TimeStamp(serial).timeTime()
                     if mtime > latest:
                         latest = mtime
             refs(p, oids)
 
     return latest
-
diff --git a/src/Products/ZopeVersionControl/Version.py b/src/Products/ZopeVersionControl/Version.py
index ba34131..87296d4 100644
--- a/src/Products/ZopeVersionControl/Version.py
+++ b/src/Products/ZopeVersionControl/Version.py
@@ -13,20 +13,16 @@
 
 __version__='$Revision: 1.11 $'[11:-2]
 
-import tempfile
 import time
-from cStringIO import StringIO
-from cPickle import Pickler, Unpickler
 
-from Acquisition import Implicit, aq_parent, aq_inner, aq_base
+from Acquisition import Implicit, aq_base
 from App.class_init import default__class_init__ as InitializeClass
 from Persistence import Persistent
 from AccessControl import ClassSecurityInfo
-from BTrees.OOBTree import OOBTree
 from OFS.SimpleItem import SimpleItem
-
-from Utility import VersionControlError
-from nonversioned import listNonVersionedObjects, removeNonVersionedData
+from ZODB._compat import BytesIO
+from ZODB._compat import Pickler, Unpickler
+from .nonversioned import listNonVersionedObjects, removeNonVersionedData
 
 
 def cloneByPickle(obj, ignore_list=()):
@@ -40,7 +36,7 @@ def cloneByPickle(obj, ignore_list=()):
         ignore_dict[id(o)] = o
 
     def persistent_id(ob, ignore_dict=ignore_dict):
-        if ignore_dict.has_key(id(ob)):
+        if id(ob) in ignore_dict:
             return 'ignored'
         if getattr(ob, '_p_changed', 0) is None:
             ob._p_changed = 0
@@ -54,7 +50,7 @@ def persistent_load(ref):
         placeholder.id = "ignored_subobject"
         return placeholder
 
-    stream = StringIO()
+    stream = BytesIO()
     p = Pickler(stream, 1)
     p.persistent_id = persistent_id
     p.dump(obj)
diff --git a/src/Products/ZopeVersionControl/VersionHistory.py b/src/Products/ZopeVersionControl/VersionHistory.py
index 7145b68..340a9d5 100644
--- a/src/Products/ZopeVersionControl/VersionHistory.py
+++ b/src/Products/ZopeVersionControl/VersionHistory.py
@@ -11,18 +11,17 @@
 #
 ##############################################################################
 
-__version__='$Revision: 1.4 $'[11:-2]
-
-from App.class_init import default__class_init__ as InitializeClass
-from Persistence import Persistent
+from .EventLog import EventLog, LogEntry
+from .Utility import VersionControlError
+from .ZopeVersion import ZopeVersion
 from AccessControl import ClassSecurityInfo
-from EventLog import EventLog, LogEntry
-from Utility import VersionControlError
-from ZopeVersion import ZopeVersion
-from BTrees.IOBTree import IOBTree
+from Acquisition import Implicit
+from App.class_init import default__class_init__ as InitializeClass
 from BTrees.IIBTree import IIBTree
+from BTrees.IOBTree import IOBTree
 from BTrees.OOBTree import OOBTree
-from Acquisition import Implicit
+from Persistence import Persistent
+
 import time
 
 MAX32 = int(2**31 - 1)
@@ -87,7 +86,7 @@ def labelVersion(self, version_id, label, force=0):
     def createBranch(self, branch_id, version_id):
         """Create a new branch associated with the given branch_id. The
            new branch is rooted at the version named by version_id."""
-        if self._branches.has_key(branch_id):
+        if branch_id in self._branches:
             raise VersionControlError(
                 'Activity already exists: %s' % branch_id
                 )
@@ -135,7 +134,7 @@ def createVersion(self, object, branch_id):
     security.declarePrivate('hasVersionId')
     def hasVersionId(self, version_id):
         """Return true if history contains a version with the given id."""
-        return self._versions.has_key(version_id)
+        return version_id in self._versions
 
     security.declarePrivate('isLatestVersion')
     def isLatestVersion(self, version_id, branch_id):
diff --git a/src/Products/ZopeVersionControl/VersionSupport.py b/src/Products/ZopeVersionControl/VersionSupport.py
index 3e80f07..654c226 100644
--- a/src/Products/ZopeVersionControl/VersionSupport.py
+++ b/src/Products/ZopeVersionControl/VersionSupport.py
@@ -11,13 +11,13 @@
 #
 ##############################################################################
 
-__version__='$Revision: 1.4 $'[11:-2]
-
-import ExtensionClass, AccessControl, Acquisition
+from .Utility import use_vc_permission
+from .Utility import VersionControlError, isAVersionableResource
 from App.class_init import default__class_init__ as InitializeClass
 from App.special_dtml import DTMLFile
-from Utility import VersionControlError, isAVersionableResource
-from Utility import use_vc_permission
+
+import AccessControl
+import ExtensionClass
 
 
 class VersionSupport(ExtensionClass.Base):
diff --git a/src/Products/ZopeVersionControl/ZopeRepository.py b/src/Products/ZopeVersionControl/ZopeRepository.py
index 608c68d..eb50794 100644
--- a/src/Products/ZopeVersionControl/ZopeRepository.py
+++ b/src/Products/ZopeVersionControl/ZopeRepository.py
@@ -11,12 +11,13 @@
 #
 ##############################################################################
 
+from . import Repository
+from .SequenceWrapper import SequenceWrapper
 from App.class_init import default__class_init__ as InitializeClass
 from App.special_dtml import DTMLFile
-from SequenceWrapper import SequenceWrapper
+
 import AccessControl
 import OFS
-import Repository
 
 # BBB Zope 2.12
 try:
@@ -77,7 +78,7 @@ def __getitem__(self, name):
         history = self._histories.get(name)
         if history is not None:
             return history.__of__(self)
-        raise KeyError, name
+        raise KeyError(name)
 
     security.declarePrivate('objectIds')
     def objectIds(self, spec=None):
diff --git a/src/Products/ZopeVersionControl/ZopeVersion.py b/src/Products/ZopeVersionControl/ZopeVersion.py
index 58b6f5a..97c99a0 100644
--- a/src/Products/ZopeVersionControl/ZopeVersion.py
+++ b/src/Products/ZopeVersionControl/ZopeVersion.py
@@ -11,10 +11,12 @@
 #
 ##############################################################################
 
+from . import Version
 from App.class_init import default__class_init__ as InitializeClass
 from App.special_dtml import DTMLFile
-import OFS, AccessControl
-import Version
+
+import OFS
+import AccessControl
 
 # BBB Zope 2.12
 try:
diff --git a/src/Products/ZopeVersionControl/ZopeVersionHistory.py b/src/Products/ZopeVersionControl/ZopeVersionHistory.py
index a2505a7..f20d557 100644
--- a/src/Products/ZopeVersionControl/ZopeVersionHistory.py
+++ b/src/Products/ZopeVersionControl/ZopeVersionHistory.py
@@ -11,10 +11,12 @@
 #
 ##############################################################################
 
+from . import VersionHistory
 from App.class_init import default__class_init__ as InitializeClass
 from App.special_dtml import DTMLFile
-import OFS, AccessControl
-import VersionHistory
+
+import AccessControl
+import OFS
 
 # BBB Zope 2.12
 try:
@@ -73,7 +75,7 @@ def __getitem__(self, name):
         activity = self._branches.get(name)
         if activity is not None:
             return activity.__of__(self)
-        raise KeyError, name
+        raise KeyError(name)
 
     security.declarePrivate('objectIds')
     def objectIds(self, spec=None):
diff --git a/src/Products/ZopeVersionControl/__init__.py b/src/Products/ZopeVersionControl/__init__.py
index 4ea203c..ab9128c 100644
--- a/src/Products/ZopeVersionControl/__init__.py
+++ b/src/Products/ZopeVersionControl/__init__.py
@@ -11,10 +11,11 @@
 #
 ##############################################################################
 
-import ZopeRepository
+from . import ZopeRepository
 from App.class_init import default__class_init__ as InitializeClass
 from App.ImageFile import ImageFile
 
+
 def initialize(context):
 
     context.registerClass(
@@ -35,7 +36,7 @@ def initialize(context):
 def install_hack():
     # Hackery - don't try this at home, kids. :) This is temporary for
     # testing purposes only.
-    from VersionSupport import VersionSupport
+    from .VersionSupport import VersionSupport
     import OFS.SimpleItem, App.Management
 
     method = App.Management.Tabs.filtered_manage_options
diff --git a/src/Products/ZopeVersionControl/nonversioned.py b/src/Products/ZopeVersionControl/nonversioned.py
index 2120b2b..71e8439 100644
--- a/src/Products/ZopeVersionControl/nonversioned.py
+++ b/src/Products/ZopeVersionControl/nonversioned.py
@@ -15,13 +15,11 @@
 $Id$
 """
 
+from .interfaces import INonVersionedData
+from .VersionSupport import isAVersionableResource
 from Acquisition import aq_base
 from OFS.ObjectManager import ObjectManager
-
-from interfaces import INonVersionedData
-from VersionSupport import isAVersionableResource
-from zope.interface import implements
-
+from zope.interface import implementer
 
 try:
     # Optional support for references.
@@ -69,10 +67,10 @@ def restoreNonVersionedData(obj, dict):
 
 
 
+@implementer(INonVersionedData)
 class StandardNonVersionedDataAdapter:
     """Non-versioned data adapter for arbitrary things.
     """
-    implements(INonVersionedData)
 
     def __init__(self, obj):
         self.obj = obj
@@ -101,14 +99,14 @@ def getNonVersionedData(self):
 
     def restoreNonVersionedData(self, data):
         for attr in self.attrs:
-            if data.has_key(attr):
+            if attr in data:
                 setattr(aq_base(self.obj), attr, data[attr])
 
 
+@implementer(INonVersionedData)
 class ObjectManagerNonVersionedDataAdapter(StandardNonVersionedDataAdapter):
     """Non-versioned data adapter for object managers.
     """
-    implements(INonVersionedData)
 
     def listNonVersionedObjects(self):
         contents = self.getNonVersionedData()['contents']
@@ -124,7 +122,7 @@ def removeNonVersionedData(self):
             removed[name] = 1
         if obj._objects:
             obj._objects = tuple([info for info in obj._objects
-                                  if not removed.has_key(info['id'])])
+                                  if info['id'] not in removed])
 
     def getNonVersionedData(self):
         contents = {}
@@ -154,7 +152,7 @@ def restoreNonVersionedData(self, data):
             ignore[name] = 1
         # Restore the items of the container.
         for name, value in data['contents'].items():
-            if not ignore.has_key(name):
+            if name not in ignore:
                 obj._setOb(name, aq_base(value))
                 if not hasattr(obj, '_tree'):
                     # Avoid generating events, since nothing was ever really
diff --git a/src/Products/ZopeVersionControl/tests/common.py b/src/Products/ZopeVersionControl/tests/common.py
index 0f31478..e6ac615 100644
--- a/src/Products/ZopeVersionControl/tests/common.py
+++ b/src/Products/ZopeVersionControl/tests/common.py
@@ -26,7 +26,6 @@ def common_setUp(self):
     # Install a hack to make SimpleItem version aware, so that the
     # tests work. In normal development, you would mix in the
     # VersionSupport class on an as-needed basis.
-    import cStringIO
     from AccessControl.SecurityManagement import newSecurityManager
     from OFS.Application import Application
     from OFS.DTMLDocument import addDTMLDocument
@@ -38,7 +37,11 @@ def common_setUp(self):
 
     from Products.ZopeVersionControl.ZopeRepository import addRepository
     from ZODB import DB
+    from ZODB._compat import PY3
     from ZODB.DemoStorage import DemoStorage
+
+    from six import StringIO
+
     s = DemoStorage()
     self.connection = DB( s ).open()
     try:
@@ -46,7 +49,7 @@ def common_setUp(self):
         a = Application()
         r['Application'] = a
         self.root = a
-        responseOut = self.responseOut = cStringIO.StringIO()
+        responseOut = self.responseOut = StringIO()
         self.app = makerequest( self.root, stdout=responseOut )
         self.app.acl_users.userFolderAddUser('UnitTester', '123', (), ())
         manage_addFolder(self.app, 'folder1')
diff --git a/src/Products/ZopeVersionControl/tests/testReferenceVersioning.py b/src/Products/ZopeVersionControl/tests/testReferenceVersioning.py
index 5a4b583..385b535 100644
--- a/src/Products/ZopeVersionControl/tests/testReferenceVersioning.py
+++ b/src/Products/ZopeVersionControl/tests/testReferenceVersioning.py
@@ -16,8 +16,8 @@
 """
 import unittest
 
-from common import common_setUp
-from common import common_tearDown
+from .common import common_setUp
+from .common import common_tearDown
 
 has_refs = 1
 try:
diff --git a/src/Products/ZopeVersionControl/tests/testVersionControl.py b/src/Products/ZopeVersionControl/tests/testVersionControl.py
index d410bfe..9ce3a08 100644
--- a/src/Products/ZopeVersionControl/tests/testVersionControl.py
+++ b/src/Products/ZopeVersionControl/tests/testVersionControl.py
@@ -16,10 +16,10 @@
 """
 import unittest
 
-from common import get_transaction
-from common import common_setUp
-from common import common_tearDown
-from common import common_commit
+from .common import get_transaction
+from .common import common_setUp
+from .common import common_tearDown
+from .common import common_commit
 
 class VersionControlTests(unittest.TestCase):
 
diff --git a/src/Products/ZopeVersionControl/tests/testVersionHistory.py b/src/Products/ZopeVersionControl/tests/testVersionHistory.py
index c40df85..75581a2 100644
--- a/src/Products/ZopeVersionControl/tests/testVersionHistory.py
+++ b/src/Products/ZopeVersionControl/tests/testVersionHistory.py
@@ -16,8 +16,8 @@
 """
 import unittest
 
-from common import common_setUp
-from common import common_tearDown
+from .common import common_setUp
+from .common import common_tearDown
 
 
 class VersionHistoryTests(unittest.TestCase):
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..18796b9
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,59 @@
+[tox]
+envlist =
+    # flake8,
+    py27,
+    py34,
+    py35,
+    py36,
+    # isort,
+    coverage-report,
+
+skip_missing_interpreters = False
+
+[testenv]
+usedevelop = True
+extras =
+    develop
+    test
+
+install_command = pip install --no-cache-dir --no-binary=:all: {opts} {packages}
+
+commands =
+    coverage run {envbindir}/zope-testrunner --path=src --all {posargs:-pvc}
+deps =
+    .[test]
+    zope.testrunner
+    coverage
+setenv =
+    PIP_NO_CACHE = 1
+    COVERAGE_FILE=.coverage.{envname}
+
+[testenv:coverage-report]
+basepython = python2.7
+deps = coverage
+setenv =
+    COVERAGE_FILE=.coverage
+skip_install = true
+commands =
+    coverage erase
+    coverage combine
+    coverage html -i
+    coverage xml -i
+    coverage report -i
+
+[testenv:isort]
+basepython = python2.7
+deps = isort
+commands =
+    isort --check-only --recursive {toxinidir}/src {toxinidir}/tests {posargs}
+
+[testenv:isort-apply]
+basepython = python2.7
+deps = isort
+commands =
+    isort --apply --recursive {toxinidir}/src {toxinidir}/tests {posargs}
+
+[testenv:flake8]
+basepython = python2.7
+deps = flake8
+commands = flake8 --doctests src tests setup.py