Review pup-packaged venv interactions

[tmontes]

Leaving this here, following up on last Monday's quick chat and recent experiments:

• Current (preliminary) status and pup-packaged Mu is not bundling venv-wheels.
• This leads to downloads on first launch.
• These downloads are downloaded into the mu/wheels package.
• They are not removed from disk on uninstall -- on Windows!

Something for us to track and, I figure, something that can easily be fixed between me and @tjguk.

[tmontes]

THOUGHTS:

• Moving this to 1.1.0b2 -- 1.1.0b1 has sailed away, already.
• Partially addressed in Bring the downloaded wheels along when creating the mu wheel #1264 -- partially because if ever Mu downloads wheels, it's downloading them to a non-safe place (can be read-only, for example, in system-wide installations).