Currently this is impossible to solve directly from this library as requests itself is at fault, as it does not provide facilities in the SessionRedirectMixin.resolve_redirects to call prepare_auth on the local PreparedRequest object to recalculate the OAuth signatures. This can probably be called after the prepare_cookies call.
Edit: can probably be done by overriding the send method so that it calls prepare_auth again, but that's hideous.
Then why aren't you opening this issue on requests?
Just giving this group a heads up before I go ahead and do it, as that issue only seem to affect OAuth1 due to its signature requirements.
Assuming this is resolved in new versions of requests + #118. Closing.
Please re-open if this is not the case.