Add better error reporting for Grouper interactions.

Something mentioned to me in Slack by Mark Fischer:

"Just a note from debugging my own interactions with grouper, tossing a try: except block around the json decoding, and then printing the raw response from grouper in the exception handling helped a lot in debugging."

This could be used anywhere an rsp.json() call is being made to parse a Grouper REST response, e.g. in grouper_query.py and in the synchronize() method in delta.py.

Benefit would be more visibility for Mark's team over in UITS if/when Grouper barfs on a request, which has happened occasionally.

[zensense]

I second this, the error reporting in the PG scripts sucks.