python - pq: Raise the exception, not return.

Log Message:
-----------
Raise the exception, not return.

Modified Files:
--------------
pq/src:
client3.py (r1.18 -> r1.19)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/pq/src/client3.py.diff?r1=1.18&r2=1.19)