pgsql: plpython: Code cleanup related to removal of Python 2 support.

plpython: Code cleanup related to removal of Python 2 support.

Since 19252e8ec93 we reject Python 2 during build configuration. Now that the
dust on the buildfarm has settled, remove Python 2 specific code, including
the "Python 2/3 porting layer".

The code to detect conflicts between plpython using Python 2 and 3 is not
removed, in case somebody creates an out-of-tree version adding back support
for Python 2.

Reviewed-By: Peter Eisentraut <peter(at)eisentraut(dot)org>
Reviewed-By: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/20211031184548.g4sxfe47n2kyi55r@alap3.anarazel.de

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/9b7e24a2cb37fb52af13219f625cd719e364a346

Modified Files
--------------
contrib/hstore_plpython/hstore_plpython.c | 12 +++----
contrib/jsonb_plpython/jsonb_plpython.c | 27 ++++++--------
contrib/ltree_plpython/ltree_plpython.c | 6 +---
src/pl/plpython/plpy_cursorobject.c | 8 ++---
src/pl/plpython/plpy_elog.c | 26 ++++++--------
src/pl/plpython/plpy_exec.c | 44 +++++++++++------------
src/pl/plpython/plpy_main.c | 59 ++++++-------------------------
src/pl/plpython/plpy_planobject.c | 2 +-
src/pl/plpython/plpy_plpymodule.c | 32 +++++------------
src/pl/plpython/plpy_plpymodule.h | 2 --
src/pl/plpython/plpy_resultobject.c | 16 +++------
src/pl/plpython/plpy_spi.c | 10 +++---
src/pl/plpython/plpy_typeio.c | 40 +++++++++------------
src/pl/plpython/plpy_util.c | 9 -----
src/pl/plpython/plpy_util.h | 2 --
src/pl/plpython/plpython.h | 34 +-----------------
16 files changed, 95 insertions(+), 234 deletions(-)