Feature/fix misparsed tokens

[fluffy-critter]

Summary

Fixes exception recursion error when handling a bad Authorization header; fixes #466

Detailed description

When a token failed due to malformed/expired token or malformed header, this would result in an error page. But the error handler was also trying to get the active user, which in turn was trying to parse the bad header. This led to an overall failure.

The fix was to make use of the already-existing token_error field on the context which informs us that the token already failed to parse, and to make user.get_active() return None.

Developer/user impact

Test plan

Manually tested with invalid, expired, malformed, and valid tokens via curl -H.

Got a site to show off?

[fluffy-critter]

I have really got to start unit testing this stuff