Arcyd: log errors when reporting exceptions
Arcyd: log errors when reporting exceptions

Update the existing messaging exception handler to also log errors when
reporting.

Test Plan:
Just in case I missed something
$ ./precommit.sh

Exercise the changed code directly with
.. change bad_git_push_arcyd.py to fail all fetches ..
$ ./testbed/arcyd/unreliable_git_loop_test.sh
    .. wait long enough for fetch fail to escalate to handler ..
    .. stop and examine log output to make sure is as expected ..

cs-shadow/phabricator-tools,aevri/phabricator-tools,aevri/phabricator-tools,aevri/phabricator-tools,kjedruczyk/phabricator-tools,bloomberg/phabricator-tools,cs-shadow/phabricator-tools,bloomberg/phabricator-tools,kjedruczyk/phabricator-tools,valhallasw/phabricator-tools,bloomberg/phabricator-tools,cs-shadow/phabricator-tools,valhallasw/phabricator-tools,cs-shadow/phabricator-tools,kjedruczyk/phabricator-tools,kjedruczyk/phabricator-tools,bloomberg/phabricator-tools,aevri/phabricator-tools,bloomberg/phabricator-tools,valhallasw/phabricator-tools,aevri/phabricator-tools,cs-shadow/phabricator-tools,kjedruczyk/phabricator-tools,valhallasw/phabricator-tools