[Fixed]-('Unexpected credentials type', None, 'Expected', 'service_account') with oauth2client (Python)

I too was running in to this. The fix in my case was to use the correct json file. I needed to use the one that was saved when I created the service account key, not the one with the service account client:

Hope that helps!

It seams like the sample in google-api-python-client has it right

google-api-python-client/tree/master/samples/analytics