Fix issue with postmortem debugging. (submitted by 'Sundance')
Fix issue with postmortem debugging. (submitted by 'Sundance')

There seems to be a little bug in pudb.pm(). pm() calls port_mortem()
with a traceback object as its argument, where post_mortem() expects a
full exception info tuple.

amigrave/pudb,albfan/pudb,amigrave/pudb,albfan/pudb