python - be: Handle AbortTransaction exceptions.

Log Message:
-----------
Handle AbortTransaction exceptions.

Modified Files:
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be/src:
xact.c (r1.1 -> r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/xact.c.diff?r1=1.1&r2=1.2)
prime.py (r1.13 -> r1.14)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/prime.py.diff?r1=1.13&r2=1.14)