Fixed import error handling when application tests are stored in a tests directory, rather than a tests.py file.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5180 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/test/simple.py

@@ -49,8 +49,11 @@ def build_suite(app_module):
             pass
         else:
             # The module exists, so there must be an import error in the 
-            # test module itself. We don't need the module; close the file
-            # handle returned by find_module.
+            # test module itself. We don't need the module; so if the
+            # module was a single file module (i.e., tests.py), close the file
+            # handle returned by find_module. Otherwise, the test module
+            # is a directory, and there is nothing to close.
+            if mod[0]:
                 mod[0].close()
             raise