Registration should issue error message if backend returns error

[joequant]

I have someone try to register from Tunisia but got blocked because the backend
disallowed the country. The issue is that when there is an invalid response from
the backend, the system just does nothing, and an error box would be useful.

[taffyatom]

thx, will fix it

[joequant]

Also the frontend seems to ignore the msg that comes with the 400 error which is unfortunate since that message is useful for why the login failed. Can you point me to roughly where in the code the system handles 400 errors since I can put in a pull request.

[taffyatom]

what errors do you mean?