Install pack dependencies using a custom pypi mirror?


I would like to know if there is a way to setup Stackstorm to use a custom pypi mirror to install pack dependencies ?
We have internal ones that are not published publicly and so far I could not find a way to do this ?

I found this Packs — StackStorm 3.1.0 documentation
But AFAIK this will not do anything about getting the rependencies from requirements.txt from a specific pypi mirror.
Same for this: Packs — StackStorm 3.1.0 documentation


From Slack : Setting up /etc/pip.conf on the host should do it.