Index: Lib/test/test_importhooks.py
===================================================================
--- Lib/test/test_importhooks.py	(révision 76228)
+++ Lib/test/test_importhooks.py	(copie de travail)
@@ -143,15 +143,14 @@
         self.meta_path = sys.meta_path[:]
         self.path_hooks = sys.path_hooks[:]
         sys.path_importer_cache.clear()
-        self.modules_before = sys.modules.copy()
+        self.modules_before = support.modules_setup()
 
     def tearDown(self):
         sys.path[:] = self.path
         sys.meta_path[:] = self.meta_path
         sys.path_hooks[:] = self.path_hooks
         sys.path_importer_cache.clear()
-        sys.modules.clear()
-        sys.modules.update(self.modules_before)
+        support.modules_cleanup(*self.modules_before)
 
 
 class ImportHooksTestCase(ImportHooksBaseTestCase):
Index: Lib/test/test_pkg.py
===================================================================
--- Lib/test/test_pkg.py	(révision 76228)
+++ Lib/test/test_pkg.py	(copie de travail)
@@ -48,13 +48,11 @@
         self.root = None
         self.pkgname = None
         self.syspath = list(sys.path)
-        self.sysmodules = sys.modules.copy()
+        self.modules_before = support.modules_setup()
 
     def tearDown(self):
         sys.path[:] = self.syspath
-        sys.modules.clear()
-        sys.modules.update(self.sysmodules)
-        del self.sysmodules
+        support.modules_cleanup(*self.modules_before)
         cleanout(self.root)
 
         # delete all modules concerning the tested hiearchy
Index: Lib/test/support.py
===================================================================
--- Lib/test/support.py	(révision 76228)
+++ Lib/test/support.py	(copie de travail)
@@ -951,7 +951,24 @@
               (module.__name__, t))
     return f, t
 
+
 #=======================================================================
+# Support for saving and restoring the imported modules.
+
+def modules_setup():
+    return sys.modules.copy(),
+
+def modules_cleanup(oldmodules):
+    # Encoders/decoders are registered permanently within the internal
+    # codec cache. If we destroy the corresponding modules their
+    # globals will be set to None which will trip up the cached functions.
+    encodings = [(k, v) for k, v in sys.modules.items()
+                 if k.startswith('encodings.')]
+    sys.modules.clear()
+    sys.modules.update(encodings)
+    sys.modules.update(oldmodules)
+
+#=======================================================================
 # Threading support to prevent reporting refleaks when running regrtest.py -R
 
 # NOTE: we use thread._count() rather than threading.enumerate() (or the