(py-execute-region): If the line at the beginning of the region is a

(py-execute-region): If the line at the beginning of the region is a
#! line, use the command on that line as the shell command to use to
execute the region.  I.e. if the region looks like

----------------
#! /usr/bin/env python1.5

print 'hello world'.startswith('hello')
----------------

you'll get an exception! :)

This closes SF bug #232398.