This seems to be a problem only for python 2.7 (although possibly python 3 too as I am blocked by https://github.com/google/oauth2client/issues/106 so I might not have got that far with python 3).
I've gotten word internally at Google that the root cause of this has been remedied - is that what everyone's observing externally? And workarounds are no longer required?
Reported here: https://github.com/burnash/gspread/issues/239 for details, but in -----BEGIN PRIVATE KEY-----\n*\n-----END PRIVATE KEY-----\n", it seems * must not contain \u003d
This seems to be a problem only for python 2.7 (although possibly python 3 too as I am blocked by https://github.com/google/oauth2client/issues/106 so I might not have got that far with python 3).