Update py-setuptools to 20.6.7.

v20.6.7
-------

* Issue #523: Disabled support for environment markers
  introduced in v20.5.

v20.6.6
-------

* Issue #503: Restore support for PEP 345 environment
  markers by updating to Packaging 16.6.

v20.6.0
-------

* New release process that relies on
  `bumpversion <https://github.com/peritus/bumpversion>`_
  and Travis CI for continuous deployment.
* Project versioning semantics now follow
  `semver <https://semver.org>`_ precisely.
  The 'v' prefix on version numbers now also allows
  version numbers to be referenced in the changelog,
  e.g. https://pythonhosted.org/setuptools/history.html#v20-6-0.

20.5
----

* BB Pull Request #185: Add support for environment markers
  in requirements in install_requires, setup_requires,
  tests_require as well as adding a test for the existing
  extra_requires machinery.

20.4
----

* Issue #422: Moved hosting to
  `Github <https://github.com/pypa/setuptools>`_
  from `Bitbucket <https://bitbucket.org/pypa/setuptools>`_.
  Issues have been migrated, though all issues and comments
  are attributed to bb-migration. So if you have a particular
  issue or issues to which you've been subscribed, you will
  want to "watch" the equivalent issue in Github.
  The Bitbucket project will be retained for the indefinite
  future, but Github now hosts the canonical project repository.

20.3.1
------

* Issue #519: Remove import hook when reloading the
  ``pkg_resources`` module.
* BB Pull Request #184: Update documentation in ``pkg_resources``
  around new ``Requirement`` implementation.

20.3
----

* BB Pull Request #179: ``pkg_resources.Requirement`` objects are
  now a subclass of ``packaging.requirements.Requirement``,
  allowing any environment markers and url (if any) to be
  affiliated with the requirement
* BB Pull Request #179: Restore use of RequirementParseError
  exception unintentionally dropped in 20.2.


(wiz)