Avoid Python memory leaks in hstore_plpython and jsonb_plpython.
Fix some places where we might fail to do Py_DECREF() on a Python
object (thereby leaking it for the rest of the session). Almost
all of the risks were in error-recovery paths, which we don't really
expect to hit anyway. Hence, while this is definitely a bug fix,
it doesn't quite seem worth back-patching.
Nikita Glukhov, Michael Paquier, Tom Lane
Discussion: https://postgr.es/m/
28053a7d-10d8-fc23-b05c-
b4749c873f63@postgrespro.ru