Re: fix crash with Python 3.11

On Wed, 2021-12-22 at 09:24 +0100, Peter Eisentraut wrote:
> The fix is that we need to catch the PostgreSQL error and turn it into a 
> Python exception, like we do for other places where plpy.* methods call 
> into PostgreSQL internals.

Tested on Ubuntu 20.04, with 3.11.0a3 (built by hand) and 3.8.10 (from
the repositories). The tests pass, so LGTM. I agree that tidying up
some of the code duplication would be nice.

Thanks,
--Jacob