Tox relativization forces pipenv bug

[tucked]

Here is the pipenv bug: https://github.com/pypa/pipenv/issues/4588

It gets hit when passing --python .anything (i.e. interpreter path starts with "."), which this plugin does by default: https://github.com/tox-dev/tox-pipenv/blob/aec927016bb3f8edfe29d428092e47f976c47ea1/tox_pipenv/plugin.py#L67

Related: https://github.com/tox-dev/tox/issues/1339#issuecomment-759081423

A better workaround I've found, though is to use --python='{envpython}' which seems to avoid Tox relativization.