plpython: Restore alternative output for plpython_error test.

Andres Freund <andres@anarazel.de>

Commit: 43e7787dd3387a7455fc4d9c353addb79a50ebe5
Author: Andres Freund <andres@anarazel.de>
Date: 2022-03-08T18:34:06Z
Releases: 15.0
plpython: Restore alternative output for plpython_error test.

In db23464715f I removed the alternative output for plpython_error. Wrongly
so, because the output changed in Python 3.5, not Python 3.

Files