Habilitar o Python no PostgreSQL

• Cenário

Windows 10
PostgreSQL 9.5 (instalado em C:\Program Files\PostgreSQL\9.5)
Python 3.7.4 - Windows x86-64 executable installer (python-3.7.4-amd64.exe - instalado em C:\Python\Python37)

• Problema 1

Ao executar o comando:

create extension plpython3u;

Ocorre o erro:

ERROR:  could not load library "C:/Program Files/PostgreSQL/9.5/lib/plpython3.dll": unknown error 126