use packaging instead of pkg_resources to parse versions

[minrk]

Pinning setuptools as a runtime dependency is often a problem, and setting a minimum of extremely recent setuptools 60 is causing conflicts with e.g. pandas which pins setuptools<60 (this is making an unsolvable conda environment for me right now).

migration advice suggests using the lighter packaging package, and I don't see a reason to use a version pin.

The pkg_resources function is also available for at least 30 versions (setuptools 30), so the >=60 doesn't seem to have been the right number to use.

Recommend a patch release with the fix, since the dependency in 6.11 is causing installation problems.

[bollwyvl]

Ick:

         File "/tmp/pip-download-q4sqesd9/ipyparallel_89b290df93ac4e98934f08ef9634b493/setupbase.py", line 37, in <module>
          from setuptools.config import StaticModule
      ImportError: cannot import name 'StaticModule' from 'setuptools.config' (/tmp/pip-build-env-tf4je9_5/overlay/lib/python3.9/site-packages/setuptools/config/__init__.py)
      [end of output]

[bollwyvl]

ugh, it's the homebrew get_version in setupbase (which has propagated to jupyter_packaging)... i don't think that's can be blocker here, though, if other stuff is broken downstream...

[blink1073]

Thanks!

[minrk]

I fixed the setuptools 61 issue in ipyparallel in ipython/ipyparallel#680 , just need to make a release.