Handle internal server errors in frontend.

[dpordomingo]

There are some URLs that can return a 500 error without being caught by the frontend, so the site will show a meaningless plain error message like the following one received from /oauth-callback when GitHub auth fails

The frontend should be able to catch those errors.

[bzz]

It's a bit hard to understand the current status of this issue - from the first sight, it has 2 PRs and both need to be rebased and both need to be reviewed..

Could somebody please summarize the status here please?

[smacker]

PRs description explains difference quite well. I have rebased my PR.

[dpordomingo]

Issue will be solved by original PR #142 and the new issue #201