Provide a specific error for connection related issue

[sevdog]

Expected behaviour

Whenever a network/connection problem it could be useful to distinguish it directly from a logic authentication error.
This could improve filtering based on exception type (ie: to handle logging in django integration).

Actual behaviour

Currently the wrapper on remote requests intercepts connection-related exceptions and transforms them into generic AuthFailed exceptions, masking the underlaying exception.

social-core/social_core/backends/base.py

Lines 244 to 245 in 95316b0

	except ConnectionError as err:
	raise AuthFailed(self, str(err))

Currently the only method to distinguish this case by using the __cause__ attribute which involves more code than a try-except.

What are the steps to reproduce this issue?

1. be offline
2. try to connect to a provider which is not hosted on your host

OR

1. create a self-signed SSL cert for a local provider
2. configure provider to be used without bypassing cert verification
3. try to connect to that provider

In both cases we are going to receive a simple AuthFailed exception and we need to parse the message to identify what happened.