lib2to3 package is deprecated

Hi! Thank you for the great tool!

Running it on Python 3.11.0 emits following warning:

```
.../python-3.11.0/lib/python3.11/site-packages/unify.py:125: DeprecationWarning: lib2to3 package is deprecated and may not be able to parse Python 3.10+
  from lib2to3.pgen2 import tokenize as lib2to3_tokenize
```

Everything works as expected though. Just wanted to let you know.