Added missing recommendations command and cleaned up code

[inclement]

Added this missing command, which existed in the argument parser but wasn't actually implemented.

Not sure what format we really want, but just having the command available is probably an improvement for now.

I thought about removing the argument entirely, but it does seem useful to be able to print the p4a recommendations easily.

[inclement]

Also updated minimum python version supported to 3.6, as originally agreed in #1918 - it's my mistake that I left it at 3.4 in that PR. This minimum version is now essential since I added f-strings to the code.

[AndreMiras]

Looking good thanks, except the linter is crying

[inclement]

This one is also failing only on osx with the pyconfig.h error...not sure what's wrong, although it seems fairly clear this PR is not the culprit.

[inclement]

Tests failing only due to macos issue also present on trunk.

[AndreMiras]

LGTM!
And I got mislead in the other PR thinking it was the one breaking osx with python3.8, but definitely not then

[inclement]

Thanks!
Looks like we'll have to do something else about this issue breaking the develop branch tests :/

[AndreMiras]

For records, this got fixed recently via #2063