fix(python2): do not rewrite sys.path entries for PYTHONPATH

Fixes #1670

src/virtualenv/create/via_global_ref/builtin/python2/site.py

@@ -20,6 +20,7 @@ def main():
     prefix, exec_prefix = abs_path(sys.prefix), abs_path(sys.exec_prefix)
     global_site_package_enabled = config.get("include-system-site-packages", False) == "true"
     rewrite_standard_library_sys_path(base_executable, exe_dir, exec_prefix, base_prefix, prefix, base_exec_prefix)
+    revert_python_path_rewrite(base_executable, exe_dir, exec_prefix, base_prefix, prefix, base_exec_prefix)
     disable_user_site_package()
     load_host_site()
     if global_site_package_enabled:
@@ -124,6 +125,24 @@ def translate_directory(directory, base_executable, exe_dir, exec_prefix, base_p
     return directory
 
 
+def revert_python_path_rewrite(base_executable, exe_dir, exec_prefix, base_prefix, prefix, base_exec_prefix):
+    # Now that we can access os.environ["PYTHONPATH"], we can revert our
+    # rewrite of thoses paths done in `rewrite_standard_library_sys_path`.
+    import os
+
+    python_paths = os.environ.get("PYTHONPATH", "").split(":")
+    for ppath in map(abs_path, python_paths):
+        translated_ppath = translate_directory(
+            ppath, base_executable, exe_dir, exec_prefix, base_prefix, prefix, base_exec_prefix
+        )
+        try:
+            at = sys.path.index(translated_ppath)
+        except ValueError:
+            pass
+        else:
+            sys.path[at] = ppath
+
+
 def disable_user_site_package():
     """Flip the switch on enable user site package"""
     # sys.flags is a c-extension type, so we cannot monkeypatch it, replace it with a python class to flip it