only log rate limit errors when requests fail

the rate limit will be 0 for the last successful request with status 200

nbviewer/providers/github/client.py

@@ -83,7 +83,7 @@ def _log_rate_limit(self, future):
 
         remaining = int(remaining_s)
         limit = int(limit_s)
-        if remaining == 0:
+        if remaining == 0 and status >= 400:
             text = response_text(r)
             try:
                 message = json.loads(text)['message']