Add InCommon error handling.
Add InCommon error handling.

If the IdP gives insufficient attributes, lean on the InCommon service
intended to handle just that situation. This is a service announced
earlier this year. Details available at:

https://spaces.internet2.edu/display/InCCollaborate/Error+Handling+Service

tcmitchell/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal