The CI tests for dev-v2.10 and dev-v2.11 broke a few days ago with the same error

Collecting pysolr==3.9.0 (from -r requirements.txt (line 102))
  Downloading pysolr-3.9.0.tar.gz (55 kB)
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [68 lines of output]
      /tmp/pip-install-iyrzysc_/pysolr_1ac89b9533694450b0e9e43d23a237e7/.eggs/setuptools_scm-8.2.0-py3.9.egg/setuptools_scm/_integration/setuptools.py:31: RuntimeWarning:
      ERROR: setuptools==58.1.0 is used in combination with setuptools-scm>=8.x

      Your build configuration is incomplete and previously worked by accident!
      setuptools-scm requires setuptools>=61

      Suggested workaround if applicable:
       - migrating from the deprecated setup_requires mechanism to pep517/518 and using a pyproject.toml to declare build dependencies which are reliably pre-installed before running the build tools

Full error: https://gist.github.com/amercader/b047186b9ab6cab0e8e47cd87b1aeebe

Summary of a long and convoluted investigation:

• Both CKAN 2.10 and 2.11 use pysolr==3.9.0 and are tested on the python:3.9-bullseye image
• This combination no longer works because pysolr uses setuptools-scm and the latest version (8.2) does not work with the setuptools version the image has (58.*)
• All higher version Python images work, because of higher setuptools versions
• CKAN master works because pysolr 3.10.0 does not have this issue (I guess they changed the way build requirements are defined).
• So we either:
  1. Upgrade pysolr on dev-v2.10 and dev-v2.11
  2. Upgrade setuptools in our particular test environment

I went with option 2 because it's the more straightforward and less likely to break things on existing sites but happy to reconsider.

This PR targets 2.11, on 2.10 we still have the requirement-setuptools.txt file so I bumped the requirement there (0bf1c7d).

Refs:

pypa/setuptools-scm#1112
pypa/setuptools-scm#1111