vendor uncache helper in to our package.

mock/tests/support.py

@@ -1,3 +1,6 @@
+import contextlib
+import sys
+
 target = {'foo': 'FOO'}
 
 
@@ -14,3 +17,29 @@ def wibble(self): pass
 
 class X(object):
     pass
+
+
+@contextlib.contextmanager
+def uncache(*names):
+    """Uncache a module from sys.modules.
+
+    A basic sanity check is performed to prevent uncaching modules that either
+    cannot/shouldn't be uncached.
+
+    """
+    for name in names:
+        if name in ('sys', 'marshal', 'imp'):
+            raise ValueError(
+                "cannot uncache {0}".format(name))
+        try:
+            del sys.modules[name]
+        except KeyError:
+            pass
+    try:
+        yield
+    finally:
+        for name in names:
+            try:
+                del sys.modules[name]
+            except KeyError:
+                pass

mock/tests/testpatch.py

@@ -9,7 +9,7 @@
 from mock.tests import support
 from mock.tests.support import SomeClass, is_instance
 
-from test.test_importlib.util import uncache
+from .support import uncache
 from mock import (
     NonCallableMock, sentinel,
     MagicMock, Mock, NonCallableMagicMock, patch,