gnu: python-celery: Remove needless inputs.

These are indirect requirements and propagated by python-kombu.

* gnu/packages/python.scm(python-celery)[propagated-inputs] Remove python-amqp
  and python-anyjson.

gnu: Remove some outdated comments.

These comments were about setuptools used at runtime for pkg_resources.

* gnu/packages/python.scm: Remove some outdated comments.

gnu: python-tox: Update FIXME comments.

* gnu/packages/python.scm(python-tox)[arguments]: Update FIXME
  comment. [inputs]: Add FIXME comment.

gnu: python-urllib3: update comment.

* gnu/packages/python.scm(python-urllib3)[propagated-inputs]: Update comment.

gnu: python-wsgi-intercept: Correct inputs.

* gnu/packages/python.scm(python-wsgi-intercept): [native-inputs]: move
  python-six to [propagated-inputs].  [propagated-inputs] move
  python-httplib2, python-requests to [native-inputs].

gnu: python-websocket-client: Correct inputs.

* gnu/packages/python.scm (python-websocket-client)[native-inputs] change to
  [propagated-inputs], remove a wrong comment.

gnu: python-zope-security: Correct inputs.

* gnu/packages/python.scm(python-zope-security)[native-inputs] New element,
  move python-zope-component, python-zope-configuration, python-zope-location,
  python-zope-testrunner, python-zope-testing here.

gnu: python-configobj: Correct inputs.

* gnu/packages/python.scm(python-configobj)[native-inputs] change to
  [propagated-inputs].

gnu: python-zope-location: Correct inputs.

* gnu/packages/python.scm(python-zope-location)[native-inputs] change to
  [propagated-inputs].

gnu: python-zope-interface: Correct inputs.

* gnu/packages/python.scm(python-zope-interface)[propagated-inputs] change to
  [native-inputs].

gnu: python-pathpy: Build documentation.

* gnu/packages/python.scm (python-pathpy, python2-pathpy)
  [output] Add output "doc".
  [native-inputs]: Add python-sphinx and python-rst.linker
  [build-doc], [install-doc]: New build phases.

gnu: Add python-rst.linker, python2-rst.linker.

* gnu/packages/python.scm (python-rst.linker, python2-rst.linker): New
  variables.

gnu: python-numpydoc: Correct inputs.

* gnu/packages/python.scm (python-numpydoc, python-numpydoc)
  [native-inputs]: Remove python-docutils. Move python-shpinx to
  [propagated-inputs].

gnu: python-redis: Remove unused input.

* gnu/packages/python.scm (python-redis, python2-redis) Comment out
  [native-inputs] since these are used only for running tests, which
  is disabled since it requires a Redis server.

gnu: python2-scikit-image: Remove needless native-input and inheritance.

Remove last additional [native-inputs] python-mock, thus there is no
need to inherit python-scikit-image package. Simply use
package-with-python2.

* gnu/packages/python.scm: (python-scikit-image): [properties]: Remove
  python2-variant. (python2-scikit-image) Use simply
  "package-with-python2" after removing last [native-inputs] python-mock.

gnu: python2-scikit-image: Remove needless propagated-input.

* gnu/packages/python.scm: (python2-scikit-image)
  [propagated-inputs]: Remove python-pytz, it does not occur anywhere in
  the source.

gnu: python-scikit-image: Correct inputs.

* gnu/packages/python.scm: (python-scikit-image, python2-scikit-image)
  [propagated-inputs]: Move python-numpy and python-six to [native-inputs].
  Add comment.

gnu: python-blinker: No longer disable tests.

The package does not provide tests, but there is no need to disable them.
Having them enabled allows running them if some newer version may provide
tests.

* gnu/package/python.scm (python-blinker, python2-blinker):
  [arguments]: Remove.

gnu: python-feedgenerator: Remove python byte-code files from source.

* gnu/packages/python.scm (python-feedgenerator, python2-feedgenerator)
  [source]: Add snippet.

gnu: python-joblib: Add comment.

* gnu/packages/python.scm (python-joblib): Add comment.