Description

Pip is planning to use a new resolver by default from 20.3, which is more strict in it's dependency handling.

Currently, tox's mypy test environment defines this:

deps =
    {[base]deps}
    mypy==0.782
    mypy-zope

Given that input, pip>=20.3 will likely either:

1. Choose an older mypy-zope package that works with mypy==0.782, causing a regression.
2. Reject installing outright, as this stricter dependency resolver will refuse to install incompatible packages.