Fixes for python 3.10

[asottile]

I'm using a hacked up python to try and squash some bugs long before they're a problem: https://launchpad.net/~asottile/+archive/ubuntu/python3.10

Here's a quick demo:

$ python3.10 virtualenv.py venv10
Using base prefix '/usr'
New python executable in /home/asottile/workspace/virtualenv/venv10/bin/python3.10
Also creating executable in /home/asottile/workspace/virtualenv/venv10/bin/python
Installing setuptools, pip, wheel...
done.
$ venv10/bin/python --version
Python 3.10.0a0
$ venv10/bin/python -c 'import sys; print(sys.path)'
['', '/home/asottile/workspace/virtualenv/venv10/lib/python31.zip', '/home/asottile/workspace/virtualenv/venv10/lib/python3.10', '/home/asottile/workspace/virtualenv/venv10/lib/python3.10/lib-dynload', '/usr/lib/python3.10', '/home/asottile/workspace/virtualenv/venv10/lib/python3.10/site-packages']

[gaborbernat]

Feels a bit premature with the major rewrite in progress 😃

[asottile]

Mmmmm I was hoping to get this merged as a bugfix so I can fix tox (and then other things). I assume even with the rewrite some or most of this code will be necessary for continued python 2 support

[gaborbernat]

No changelog entry? 😢