release/tox.ini: no longer generate constraints for Python 3.7.

Also use python2.7 explicitly instead of python2.
For some reason, neither of those are found locally though.
So I generated the 2.7 constraints manually.

release/combine-constraints.py

@@ -28,54 +28,41 @@ def parse_file(filename):
 
 
 constraints = os.path.join(directory, "constraints.txt")
-constraints37 = os.path.join(directory, "constraints37.txt")
 constraints38 = os.path.join(directory, "constraints38.txt")
 constraints2 = os.path.join(directory, "constraints2.txt")
-for filename in (constraints2, constraints37, constraints38):
+for filename in (constraints2, constraints38):
     if not os.path.exists(filename):
         print(f"ERROR: {filename} does not exist.")
         print(
-            "Run: tox -p auto -e constraints2,constraints37,constraints38,constraints"
+            "Run: tox -p auto -e constraints2,constraints38,constraints"
         )
         sys.exit(1)
 
 c2 = parse_file(constraints2)
-c37 = parse_file(constraints37)
 c38 = parse_file(constraints38)
 
 # Gather them all in one dictionary.
 pins = defaultdict(dict)
 for package, version in c2.items():
     pins[package][2] = version
-for package, version in c37.items():
-    pins[package][37] = version
 for package, version in c38.items():
     pins[package][38] = version
 
 # Combine them.
 combi = []
 for package, versions in pins.items():
     py2_version = versions.pop(2, None)
-    py37_version = versions.pop(37, None)
     py38_version = versions.pop(38, None)
-    if py2_version == py37_version == py38_version:
+    if py2_version == py38_version:
         # All versions are the same.
         combi.append(f"{package}=={py2_version}")
         continue
     # Some versions are different or missing.
     # Start with Python 2.
     if py2_version is not None:
         combi.append(f'{package}=={py2_version}; python_version < "3.0"')
-    if not (py37_version or py38_version):
-        continue
-    if py37_version == py38_version:
-        # All Py3 versions are the same.
-        combi.append(f'{package}=={py37_version}; python_version >= "3.0"')
-        continue
-    if py37_version is not None:
-        combi.append(f'{package}=={py37_version}; python_version == "3.7"')
     if py38_version is not None:
-        combi.append(f'{package}=={py38_version}; python_version == "3.8"')
+        combi.append(f'{package}=={py38_version}; python_version >= "3.0"')
 
 output = "\n".join(combi) + "\n"
 # sanity check:

release/tox.ini

@@ -1,7 +1,6 @@
 [tox]
 envlist =
     constraints2,
-    constraints37,
     constraints38,
     constraints,
     downloads2,
@@ -14,27 +13,23 @@ skip_install = true
 commands_pre = python -m pip install -r {toxinidir}/../requirements.txt
 
 [testenv:constraints2]
-basepython = python2
+basepython = python2.7
 commands = python create-constraints.py {toxinidir}/../buildout.cfg {toxinidir}/constraints2.txt
 
-[testenv:constraints37]
-basepython = python3.7
-commands = python create-constraints.py {toxinidir}/../buildout.cfg {toxinidir}/constraints37.txt
-
 [testenv:constraints38]
 basepython = python3.8
 commands = python create-constraints.py {toxinidir}/../buildout.cfg {toxinidir}/constraints38.txt
 
 [testenv:constraints]
 basepython = python3
 # Specifying other tox envs as dependencies helps when running in parallel.
-depends = constraints2, constraints37, constraints38
+depends = constraints2, constraints38
 commands_pre =
 commands = python combine-constraints.py {toxinidir}
 
 [testenv:downloads2]
 # Use pip to download all pinned packages.
-basepython = python2
+basepython = python2.7
 depends = constraints
 commands_pre = pip install -U pip
 commands =
@@ -48,15 +43,15 @@ commands =
 #     pip download -r {toxinidir}/constraints.txt --dest {toxinidir}/dist --no-index --find-links {toxinidir}/olddist
 
 [testenv:downloads3]
-basepython = python3.7
+basepython = python3.8
 depends = constraints
 commands_pre = pip install -U pip
 commands =
-    pip download -r {toxinidir}/constraints37.txt --dest {toxinidir}/dist
+    pip download -r {toxinidir}/constraints38.txt --dest {toxinidir}/dist
 
 [testenv:gather]
 # Copy a few more files to the dist directory, for syncing with dist.plone.org.
-basepython = python3
+basepython = python3.8
 depends = downloads2, downloads3
 allowlist_externals =
     cp