Provide more detail in ERROR: Request not authorized email/message

[jonespm]

Occasionally we're getting this email message ERROR: Request not authorized

Prior to the 2.8.0 release this was ERROR: Could not find saml_user value. This was changed when djangosaml was upgraded.

This message indicates someone doesn't have access to Student Explorer and not in the group from #121. However the email doesn't indicate who doesn't have authorization, this information can be looked up from the logs. It would be useful to include this in the email message and maybe even make it less of a stack dump and more of an informational message.

[ssciolla]

Were you also thinking this would include a better message for the user?