* :memo: Update caveats section
* :white_check_mark: Update test for new pip constraint
This loosens the constraint op pip back to v21.0 (ref https://github.com/pypa/pip/issues/9139#issuecomment-782084087)
As soon as https://github.com/pypa/pip/pull/9405 is merged before the release of v21.1 planned for April, the upper constraint can be dropped altogether. Otherwise, a `pip!=21.1.*` will be needed.