Improved the error message in case of an invalid DATABASE_BACKEND to ignore…

Improved the error message in case of an invalid DATABASE_BACKEND to ignore '.svn' directories in displaying the list of valid backends

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10046 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/__init__.py

@@ -25,7 +25,8 @@ def load_backend(backend_name):
             backend_dir = os.path.join(__path__[0], 'backends')
             try:
                 available_backends = [f for f in os.listdir(backend_dir)
-                        if os.path.isdir(os.path.join(backend_dir, f))]
+                        if os.path.isdir(os.path.join(backend_dir, f))
+                        and not f.startswith('.')]
             except EnvironmentError:
                 available_backends = []
             available_backends.sort()