ci: latest pip resolver giving installation errors

[ParthS007]

Collecting iniconfig
  Downloading iniconfig-1.1.0.tar.gz (8.1 kB)
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'done'
    Preparing wheel metadata: started
    Preparing wheel metadata: finished with status 'done'
ERROR: Requested iniconfig from https://files.pythonhosted.org/packages/44/39/e96292c7f7068e58877f476908c5974dc76c37c623f1fa332fe4ed6dfbec/iniconfig-1.1.0.tar.gz#sha256=150a59361017218f4621a68ea9984772675a7f6e074ff7d02e115152f1804dc6 (from pytest<7,>=6->pytest-invenio==1.4.0->-r .min-3.6-requirements.txt (line 9)) has different version in metadata: '0.0.0'

[lnielsen]

This is happening with min requirements.

[ppanero]

Steps to reproduce:

1. Create venv
2. python -m pip install --upgrade pip setuptools py wheel redis requirements-builder Make sure you get pip>=20.3.1.
3. requirements-builder -e all --level=min setup.py > .min-3.7-requirements.txt
4. pip install -r .min-3.7-requirements.txt

Note 3.7 is because I run it on python 3.7 but you can call the file as you please.

The problem seems to come from here: https://github.com/RonnyPfannschmidt/iniconfig/blob/46322d8eb19170d43c36d4c653c8f9090b14b42c/setup.py#L10

The fact that the package does not establish a clear version.