Fixed error external user not able to login via nickname when local user has chosen the same nickname. This fix try to externally authenticate the user by trying both the email corresponding to the local nickname (when it exists), and directly with the nickname.
Fixed error external user not able to login via nickname when local user has chosen
the same nickname. This fix try to externally authenticate the user by trying both the email corresponding
to the local nickname (when it exists), and directly with the nickname.

tiborsimko/invenio-accounts,inspirehep/invenio-accounts,tiborsimko/invenio-accounts,inveniosoftware/invenio-accounts,inveniosoftware/invenio-accounts,inveniosoftware/invenio-accounts,inspirehep/invenio-accounts,inspirehep/invenio-accounts,tiborsimko/invenio-accounts