pip install -e fails on version 50: command class <class 'setuptools.command.egg_info.egg_info'> must subclass Command

> pip install -e .
    ERROR: Command errored out with exit status 1:
     command: /Users/jaykarimi/.pyenv/versions/3.6.5/envs/ci-debug/bin/python3.6 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/Users/jaykarimi/Documents/vanir/setup.py'"'"'; __file__='"'"'/Users/jaykarimi/Documents/vanir/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info
         cwd: /Users/jaykarimi/Documents/vanir/
    Complete output (19 lines):
    /Users/jaykarimi/.pyenv/versions/3.6.5/envs/ci-debug/lib/python3.6/site-packages/_distutils_hack/__init__.py:30: UserWarning: Setuptools is replacing distutils.
      warnings.warn("Setuptools is replacing distutils.")
    /Users/jaykarimi/.pyenv/versions/3.6.5/envs/ci-debug/lib/python3.6/site-packages/setuptools/dist.py:452: UserWarning: Normalizing 'v1.7.1' to '1.7.1'
      warnings.warn(tmpl.format(**locals()))
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/Users/jaykarimi/Documents/vanir/setup.py", line 127, in <module>
        setup(**_conf)
      File "/Users/jaykarimi/.pyenv/versions/3.6.5/envs/ci-debug/lib/python3.6/site-packages/setuptools/__init__.py", line 153, in setup
        return distutils.core.setup(**attrs)
      File "/Users/jaykarimi/.pyenv/versions/3.6.5/envs/ci-debug/lib/python3.6/site-packages/setuptools/_distutils/core.py", line 134, in setup
        ok = dist.parse_command_line()
      File "/Users/jaykarimi/.pyenv/versions/3.6.5/envs/ci-debug/lib/python3.6/site-packages/setuptools/_distutils/dist.py", line 484, in parse_command_line
        args = self._parse_command_opts(parser, args)
      File "/Users/jaykarimi/.pyenv/versions/3.6.5/envs/ci-debug/lib/python3.6/site-packages/setuptools/dist.py", line 903, in _parse_command_opts
        nargs = _Distribution._parse_command_opts(self, parser, args)
      File "/Users/jaykarimi/.pyenv/versions/3.6.5/envs/ci-debug/lib/python3.6/site-packages/setuptools/_distutils/dist.py", line 548, in _parse_command_opts
        "command class %s must subclass Command" % cmd_class)
    distutils.errors.DistutilsClassError: command class <class 'setuptools.command.egg_info.egg_info'> must subclass Command
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

[asmacdo]

This can be worked around with the SETUPTOOLS_USE_DISTUTILS env var. https://setuptools.readthedocs.io/en/latest/history.html#v50-0-0

I had this problem with ruamel.yaml.clib, but only when installing from source (not wheels).

Reproducer: pip install --force-reinstall --ignore-installed --no-binary :all: ruamel.yaml.clib

Snip...
distutils.errors.DistutilsClassError: command class <class 'setuptools.command.egg_info.egg_info'> must subclass Command

Workaround export SETUPTOOLS_USE_DISTUTILS="stdlib" pip install --force-reinstall --ignore-installed --no-binary :all: ruamel.yaml.clib

Collecting ruamel.yaml.clib
  Downloading https://files.pythonhosted.org/packages/92/28/612085de3fae9f82d62d80255d9f4cf05b1b341db1e180adcf28c1bf748d/ruamel.yaml.clib-0.2.0.tar.gz (178kB)
     |████████████████████████████████| 184kB 739kB/s 
Installing collected packages: ruamel.yaml.clib
    Running setup.py install for ruamel.yaml.clib ... done
Successfully installed ruamel.yaml.clib-0.2.0

[jay-karimi]

@asmacdo I can confirm that the workaround you describe with export SETUPTOOLS_USE_DISTUTILS="stdlib" seems to resolve the error I am seeing as well.