Around line 1493 in docs/pkg_resources.txt:
Return a "safe" form of a project's name, suitable for use in a
Requirement string, as a distribution name, or a PyPI project name.
All non-alphanumeric runs are condensed to single "-" characters, such that
a name like "The $$$ Tree" becomes "The-Tree". Note that if you are
generating a filename from this value you should replace the "-" characters
with underscores ("_") because setuptools and the distutils
What comes after "because setuptools and the distutils"?