Improve error handling

[KOliver94]

This PR fixes two potential problem:

• Currently message only got extracted from an exception if the exception is not an AuthException or LOG_AUTH_EXCEPTIONS is set to True. I guess this is not the intended behavior and it should affect logging, not the returned HTTP error, so I separated them to try to get the message from all types of exception and return it in the response.
• If we did not succeed to extract a message from the exception we return an empty string which can by annoying. Most of the potentially occurring exceptions are inherited from social-core's SocialAuthBaseException which in most cases define a __str__ function. So, as a fallback return the string version of the exception in the message.

[KOliver94]

Hi @st4lk,

Can you consider merging this change?

Thanks!

[st4lk]

Hey @KOliver94 ! I think it will be safer to not expose all errors to clients by default. Agree it may be useful, but there is a potential risk that some information included in error can be dangerous: the error is returned to the server that has higher permissions than the browser client. So by default such errors are not returned by API (will be logged on the server only). But there is a possibility to turn them on with REST_SOCIAL_VERBOSE_ERRORS = True settings. It is up to developer.

I've done it here: https://github.com/st4lk/django-rest-social-auth/pull/168

Available in pypi rest-social-auth v8.0.0

[KOliver94]

Great! Thank you!