A change in resolvelib broke pdm

[jmfederico]

The following change in resolvelib breaks the monkeypatching done by pdm:

sarugaku/resolvelib@eeceaf6#diff-9d16b368db940f0b65c2b9b5ba4d6ed3R71

When resolving dependencies the following error is thrown:
[TypeError]: adding_requirement() missing 1 required positional argument: 'parent'

Problem in pdm:

https://github.com/frostming/pdm/blob/927e4957360a28564a8246088c865135ccb3a784/pdm/resolver/core.py#L19

How to reproduce:

Make a clean install of pdm with newest dependencies updated: resolvelib version 0.4.0
Try to add any dependency to a project with pdm: pdm add ...

[frostming]

Already working on it, thanks for the report