`<1dev` is not a valid matcher for Python package versions in `setup.py`!

[con-f-use]

On the current master branch, you have this matcher for an install_requires package version in setup.py:

install_requires = [
    "httplib2>=0.15.0,<1dev",

The <1dev part is not a valid version specifier (edit: it is valid, just doesn't parse correctly with distlib) in the sense of PEP 440 and causes problems with a number of packing tools, as seen here:

$ python -c 'from distlib.version import NormalizedMatcher; NormalizedMatcher("httplib2>=0.15.0,<1dev")'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/jan/.local/share/virtualenvs/master_clean-V3vlFZeD/lib/python3.7/site-packages/distlib/version.py", line 125, in __init__
    vn, prefix = self.version_class(s), False
  File "/home/jan/.local/share/virtualenvs/master_clean-V3vlFZeD/lib/python3.7/site-packages/distlib/version.py", line 33, in __init__
    self._parts = parts = self.parse(s)
  File "/home/jan/.local/share/virtualenvs/master_clean-V3vlFZeD/lib/python3.7/site-packages/distlib/version.py", line 267, in parse
    result = _normalized_key(s)
  File "/home/jan/.local/share/virtualenvs/master_clean-V3vlFZeD/lib/python3.7/site-packages/distlib/version.py", line 188, in _pep_440_key
    raise UnsupportedVersionError('Not a valid version: %s' % s)
distlib.version.UnsupportedVersionError: Not a valid version: 1dev

This is just speculation, but it looks like it was either faultily auto-generated by some tool, is an incomplete copy & paste or you meant <1.dev0. However, development versions are not typically considered by tooling and it's considered bad practice to but an upper bound on python dependencies for no good reason. This should be corrected and ideally the artifact files of the effected versions fixed and re-uploaded on pypi.org.

[con-f-use]

Discussion in: googleapis/python-api-core#504