python warrant package doesnt compile with pip 10

[cawilliamson]

Issue description

This issue is related to: capless/warrant#96

The current warrant python package doesn't build and reports:

ModuleNotFoundError: No module named 'pip.req'

This appears to be due to a change in pip 10 which has changed this to pip._internal.

I suspect either pulling the latest version from devel or pulling the same version as current but using substituteInPlace to fix this would resolve (workaround) the issue but I can't get this to work. Any tips would be greatly appreciated!

Steps to reproduce

Attempt to install the warrant python package (or home-assistant since this is a dependency.)