databases/py-psycopg-pool: Add py-psycopg-pool 3.0.1

PostgreSQL database adapter for Python - Connection Pool

This distribution contains the optional connection pool package psycopg_pool.
This package is kept separate from the main psycopg package because it is likely
that it will follow a different release cycle.

WWW: https://www.psycopg.org/
WWW: https://github.com/psycopg/psycopg/tree/master/psycopg_pool