There is no specific reason for this right now, but keeping support for
old Python versions around indefinitely increases the maintenance
burden. The oldest supported Python version is now Python 2.4, which is
still shipped in RHEL/CentOS 5 by default.
In configure, add a check for the required Python version and give a
friendly error message for an old version, instead of relying on an
obscure build error later on.
Instead of calling PLy_elog() for reporting Python argument parsing
errors, generate appropriate exceptions. This matches the existing plpy
functions and is more consistent with the behavior of the Python
argument parsing routines.
In commit 5c3c3cd0a3046339597a03bc708cb5530dc07059, the new tests were
apparently just dumped into the first convenient file. Move them to a
separate file dedicated to testing that functionality and leave the
plpython_test test to test basic functionality, as it did before.
