Enable xerror in python tooling

Enable xerror in python tooling

A number of errors are explicitly handled and give reasonable errors,
but the remaining exceptions will now print the associated message from
the error map too. Errors which would previously lead to being
disconnected as the client would not understand are now received and
raised appropriately.

Change-Id: I69205b105d066f2899f7152969e96065682b0708
Reviewed-on: http://review.couchbase.org/77450
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Dave Rigby <daver@couchbase.com>
Tested-by: James Harrison <james.harrison@couchbase.com>