Fix regressions introduced by fixes for issue #27083.

Lib/importlib/_bootstrap_external.py

@@ -21,16 +21,22 @@ work. One should use importlib as the public-facing version of this module.
 # anything specified at the class level.
 
 # Bootstrap-related code ######################################################
-
+_CASE_INSENSITIVE_PLATFORMS_STR_KEY = 'win',
-_CASE_INSENSITIVE_PLATFORMS = 'win', 'cygwin', 'darwin'
+_CASE_INSENSITIVE_PLATFORMS_BYTES_KEY = 'cygwin', 'darwin'
+_CASE_INSENSITIVE_PLATFORMS =  (_CASE_INSENSITIVE_PLATFORMS_BYTES_KEY
+                                + _CASE_INSENSITIVE_PLATFORMS_STR_KEY)
 
 
 def _make_relax_case():
     if sys.platform.startswith(_CASE_INSENSITIVE_PLATFORMS):
+        if sys.platform.startswith(_CASE_INSENSITIVE_PLATFORMS_STR_KEY):
+            key = 'PYTHONCASEOK'
+        else:
+            key = b'PYTHONCASEOK'
+
         def _relax_case():
             """True if filenames must be checked case-insensitively."""
-            return (b'PYTHONCASEOK' in _os.environ
+            return key in _os.environ
-                    or 'PYTHONCASEOK' in _os.environ)
     else:
         def _relax_case():
             """True if filenames must be checked case-insensitively."""

Lib/test/test_importlib/extension/test_case_sensitivity.py

@@ -5,6 +5,7 @@ import unittest
 
 from .. import util
 
+importlib = util.import_importlib('importlib')
 machinery = util.import_importlib('importlib.machinery')
 
 
@@ -12,7 +13,7 @@ machinery = util.import_importlib('importlib.machinery')
 
 @unittest.skipIf(util.EXTENSIONS.filename is None, '_testcapi not available')
 @util.case_insensitive_tests
-class ExtensionModuleCaseSensitivityTest:
+class ExtensionModuleCaseSensitivityTest(util.CASEOKTestBase):
 
     def find_module(self):
         good_name = util.EXTENSIONS.name
@@ -26,25 +27,22 @@ class ExtensionModuleCaseSensitivityTest:
     def test_case_sensitive(self):
         with support.EnvironmentVarGuard() as env:
             env.unset('PYTHONCASEOK')
-            if b'PYTHONCASEOK' in _bootstrap_external._os.environ:
+            self.caseok_env_changed(should_exist=False)
-                self.skipTest('os.environ changes not reflected in '
-                              '_os.environ')
             loader = self.find_module()
             self.assertIsNone(loader)
 
     def test_case_insensitivity(self):
         with support.EnvironmentVarGuard() as env:
             env.set('PYTHONCASEOK', '1')
-            if b'PYTHONCASEOK' not in _bootstrap_external._os.environ:
+            self.caseok_env_changed(should_exist=True)
-                self.skipTest('os.environ changes not reflected in '
-                              '_os.environ')
             loader = self.find_module()
             self.assertTrue(hasattr(loader, 'load_module'))
 
 
 (Frozen_ExtensionCaseSensitivity,
  Source_ExtensionCaseSensitivity
- ) = util.test_both(ExtensionModuleCaseSensitivityTest, machinery=machinery)
+ ) = util.test_both(ExtensionModuleCaseSensitivityTest, importlib=importlib,
+                    machinery=machinery)
 
 
 if __name__ == '__main__':

Lib/test/test_importlib/source/test_case_sensitivity.py

@@ -11,7 +11,7 @@ import unittest
 
 
 @util.case_insensitive_tests
-class CaseSensitivityTest:
+class CaseSensitivityTest(util.CASEOKTestBase):
 
     """PEP 235 dictates that on case-preserving, case-insensitive file systems
     that imports are case-sensitive unless the PYTHONCASEOK environment
@@ -39,17 +39,10 @@ class CaseSensitivityTest:
             insensitive_finder = self.finder(insensitive_path)
             return self.find(sensitive_finder), self.find(insensitive_finder)
 
-    def env_changed(self, *, should_exist):
-        possibilities = b'PYTHONCASEOK', 'PYTHONCASEOK'
-        if any(x in self.importlib._bootstrap_external._os.environ
-                   for x in possibilities) == should_exist:
-            self.skipTest('os.environ changes not reflected in '
-                              '_os.environ')
-
     def test_sensitive(self):
         with test_support.EnvironmentVarGuard() as env:
             env.unset('PYTHONCASEOK')
-            self.env_changed(should_exist=False)
+            self.caseok_env_changed(should_exist=False)
             sensitive, insensitive = self.sensitivity_test()
             self.assertIsNotNone(sensitive)
             self.assertIn(self.name, sensitive.get_filename(self.name))
@@ -58,7 +51,7 @@ class CaseSensitivityTest:
     def test_insensitive(self):
         with test_support.EnvironmentVarGuard() as env:
             env.set('PYTHONCASEOK', '1')
-            self.env_changed(should_exist=True)
+            self.caseok_env_changed(should_exist=True)
             sensitive, insensitive = self.sensitivity_test()
             self.assertIsNotNone(sensitive)
             self.assertIn(self.name, sensitive.get_filename(self.name))

Lib/test/test_importlib/util.py

@@ -378,3 +378,12 @@ def mock_path_hook(*entries, importer):
             raise ImportError
         return importer
     return hook
+
+
+class CASEOKTestBase:
+
+    def caseok_env_changed(self, *, should_exist):
+        possibilities = b'PYTHONCASEOK', 'PYTHONCASEOK'
+        if any(x in self.importlib._bootstrap_external._os.environ
+                    for x in possibilities) != should_exist:
+            self.skipTest('os.environ changes not reflected in _os.environ')