Can't resolve dependencies in simultaneous install of two packages (dask + dask-ml)

[ravwojdyla]

Xref: dask/community#124
pip version: 21.0.1

What did you want to do?
Install two packages via github, with some dependencies (between them), at the same time, this is somewhat vague description but specifically I would like to be able to:

> pip install 'git+https:/dask/dask.git#egg=dask' 'git+https:/dask/dask-ml.git#egg=dask-ml'

This fails with dependency conflict (see the logs in the original issue), BUT interestingly as reported by @jsignell in dask/community#124 (comment), pip can install those two separately:

> pip install 'git+https:/dask/dask.git#egg=dask' 
> pip install 'git+https:/dask/dask-ml.git#egg=dask-ml'

Therefor this smells like a bug?

Output

dask/community#124 (comment)

[uranusjr]

Basically #8785

[ravwojdyla]

Thanks @uranusjr! Closing this. Btw, thank you so much for all the hard work on the new resolver!!