fix unicode py 3

Author: jimgraham

oauth2_provider/oauth2_validators.py

@@ -307,7 +307,7 @@ def save_bearer_token(self, token, request, *args, **kwargs):
         """
 
         if 'scope' not in token:
-            raise FatalClientError(u"Failed to renew access token: missing scope")
+            raise FatalClientError("Failed to renew access token: missing scope")
 
         expires = timezone.now() + timedelta(seconds=oauth2_settings.ACCESS_TOKEN_EXPIRE_SECONDS)