[Distutils] Module from install breaks subsequent install of different distribution (was: Python module for use in ‘setup.py’ but not to install)

[Ben Finney]

Ben Finney <ben+python at benfinney.id.au> writes:

> That has worked for me. But it appears to cause problems for some
> others, related to this module which should not be installed.

This discussion was prompted, for me, by this bug report
<URL:https://alioth.debian.org/tracker/index.php?func=detail&aid=314948&group_id=100328&atid=413098>.
Can someone please inspect the log output from Pip and help me
understand why an unrelated package is breaking when installing
‘python-daemon’ 2.0.3?

The ‘python-daemon’ 2.0.3 distribution declares ‘docutils’ as a
dependency with ‘setup_requires’ and ‘install_requires’. So it's
expected that asking Pip to install ‘python-daemon’ will attempt to
install ‘docutils’.

But why does the dependency install of ‘docutils’ then fail with::

=====
Downloading/unpacking docutils (from python-daemon)
  […]
  Downloading from URL https://pypi.python.org/packages/source/d/docutils/docutils-0.12.tar.gz#md5=4622263b62c5c771c03502afa3157768 (from https://pypi.python.org/simple/docutils/)
  Running setup.py (path:/home/pwj/.virtualenvs/venv/build/docutils/setup.py) egg_info for package docutils
  […]
Installing collected packages: python-daemon, lockfile, docutils
  Running setup.py install for docutils
    Running command /home/pwj/.virtualenvs/venv/bin/python -c "import setuptools, tokenize;__file__='/home/pwj/.virtualenvs/venv/build/docutils/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-7iBtrf-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/pwj/.virtualenvs/venv/include/site/python2.7
    […]
    Running docutils-0.12/setup.py -q bdist_egg --dist-dir /tmp/easy_install-XO8spm/docutils-0.12/egg-dist-tmp-0EsqLD
    Traceback (most recent call last):
      […]
      File "/home/pwj/.virtualenvs/venv/local/lib/python2.7/site-packages/pkg_resources.py", line 2147, in load
        ['__name__'])
    ImportError: No module named version
=====

Why on earth would the presence of ‘version.py’ in this distribution
cause the install of ‘docutils’ to fail? Or is some other correlation
going on? I have had other reports that subsequent attempts to install
packages also fail with the same error.

-- 
 \          “The fact that I have no remedy for all the sorrows of the |
  `\     world is no reason for my accepting yours. It simply supports |
_o__)  the strong probability that yours is a fake.” —Henry L. Mencken |
Ben Finney