Fixed #15621 -- Fixed potentially confusing error message in db backe…

…nd loading. Thanks, keegan_csmith

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15871 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/utils.py

@@ -41,6 +41,8 @@ def load_backend(backend_name):
                         and not f.startswith('.')]
             except EnvironmentError:
                 available_backends = []
+            if backend_name.startswith('django.db.backends.'):
+                backend_name = backend_name[19:] # See #15621.
             if backend_name not in available_backends:
                 error_msg = ("%r isn't an available database backend. \n" +
                     "Try using django.db.backends.XXX, where XXX is one of:\n    %s\n" +