Make sure Anitya actually looks at the OpenID errors

This would prevent a redirect loop if the OpenID endpoint
would be broken or unreachable for any of the three
"hardcoded" providers.

Signed-off-by: Patrick Uiterwijk <puiterwijk@redhat.com>
Merge pull request #41 from fedora-infra/feature/handle-flask-openid-errors

Make sure Anitya actually looks at the OpenID errors