Firstly, I would recommend this:
In your r, as a response, - check the statusCode instead of .json() then you can determine why it was rejected.
I think you need to do something like this:
session = requests.Session()
session.auth = (API_KEY, API_SECRET, ACCESS_TOKEN, ACCESS_TOKEN_SECRET)
req = session.get(url)
return req.statusCode
By splitting it up - it's clearer and allows further processing/manipulation to be easier upon response. But without knowing the twitter api, which a google of twitter api should handle, there's not much more I can offer.
And if you're dealing with JSON also include import json in your imports.