gnu: python-scipy: Declare python2-variant.

This is a followup to a50e03014177d2f00b5b85d3e1c295406f842016.

* gnu/packages/python.scm (python-scipy)[properties]: New field.

gnu: python-flake8-polyfill: Enable tests.

* gnu/packages/python.scm (python-flake8-polyfill,
python2-flake8-polyfill)[native-inputs]: Add PYTHON-FLAKE8, PYTHON-MOCK,
PYTHON-PYCODESTYLE and PYTHON-PYTEST. New field.
[arguments]: Replace 'check' phase with custom command.

gnu: python-flask-wtf: Drop failing test.

* gnu/packages/python.scm (python-flask-wtf, python2-flask-wtf)[arguments]:
Add phase to delete file that needs network access.

gnu: python-pbkdf2: Fix tests.

* gnu/packages/python.scm (python-pbkdf2)[arguments]: Replace 'check' phase
with custom command.

gnu: python-sphinx: Propagate python-requests.

* gnu/packages/python.scm (python-sphinx)[native-inputs]: Move PYTHON-REQUESTS
to ...
[propagated-inputs]: ... here.

gnu: python-pbr: Support python-sphinx>=1.2.1.

* gnu/packages/patches/python-pbr-fix-man-page-support.patch: New file.
* gnu/packages/python.scm (python-pbr-minimal): Use the new patch file.

gnu: python-qrcode: Disable tests.

* gnu/packages/python.scm (python-qrcode, python2-qrcode)[arguments]: New field.

gnu: python-sphinx-cloud-sptheme: Explicitly disable tests.

* gnu/packages/python.scm (python-sphinx-cloud-sptheme,
python2-sphinx-cloud-sptheme)[arguments]: New field.

gnu: python-sphinx-repoze-autointerface: Disable tests.

* gnu/packages/python.scm (python-sphinx-repoze-autointerface,
python2-sphinx-repoze-autointerface)[arguments]: New field.

gnu: python-sphinx-rtd-theme: Disable tests.

* gnu/packages/python.scm (python-sphinx-rtd-theme,
python2-sphinx-rtd-theme)[arguments]: New field.

gnu: python-sphinxcontrib-newsfeed: Disable tests.

* gnu/packages/python.scm (python-sphinxcontrib-newsfeed
python2-sphinxcontrib-newsfeed)[arguments]: New field.

gnu: python-sphinxcontrib-programoutput: Disable tests.

* gnu/packages/python.scm (python-sphinxcontrib-programoutput,
python2-sphinxcontrib-programoutput)[arguments]: New field.

gnu: python-tabulate: Disable tests.

* gnu/packages/python.scm (python-tabulate)[arguments]: New field.
[native-inputs]: Remove.
[source]: Remove test substitution snippet.

gnu: awscli: Explicitly disable tests.

* gnu/packages/python.scm (awscli)[arguments]: New field.
[native-inputs]: Remove.

gnu: python-mako: Fix tests.

* gnu/packages/python.scm (python-mako, python2-mako)[native-inputs]: Add
PYTHON-PYTEST.

gnu: python-openid-teams: Disable tests.

* gnu/packages/python.scm (python-openid-teams,
python2-openid-teams)[arguments]: New field.

gnu: python-openid-cla: Disable tests.

* gnu/packages/python.scm (python-openid-cla, python2-openid-cla)[arguments]:
New field.

gnu: python-pygit2: Skip tests requiring network access.

* gnu/packages/python.scm (python-pygit2, python2-pygit2)[source](patches):
New field.
* gnu/packages/patches/python-pygit2-disable-network-tests.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu: python-trollius-redis: Disable tests.

* gnu/packages/python.scm (python-trollius-redis,
python2-trollius-redis)[arguments]: New field.

Merge branch 'master' into python-tests