Improve error message for django.contrib.auth.load_backend

[Mikhail Korobov]

Hi all,

If backend can't be imported for some reason, it now raises the following message (see django.contrib.auth.__init__.py):

    except ImportError, e:
        raise ImproperlyConfigured('Error importing authentication backend %s: "%s"' % (module, e))

This message contains module name. I think it is a good idea to change this to full backend name in order to simplify debugging:

    except ImportError, e:
        raise ImproperlyConfigured('Error importing authentication backend %s: "%s"' % (path, e))

My case: custom django-registration registration backend (with supplying auth backend) that sets user.backend to wrong value (import path was incorrect, class name was correct). It was not easy to determine from existing error message which auth backend is failing because backend class name wasn't in error message.

[Russell Keith-Magee]

In [15713]:

Fixed #15532 -- Clarified the error message for unknown auth backends. Thanks to kmike for the report.

[Russell Keith-Magee]

In [15715]:

(The changeset message doesn't reference this ticket)