Rework Spack's Mercurial support (#3834)

* Add tests to mercurial package

* Add support for --insecure with mercurial fetching

* Install man pages and tab-completion scripts

* Add tests and latest version for all deps

* Flake8 fix

* Use certifi module to find CA certificate

* Flake8 fix

* Unset PYTHONPATH when running hg

* svn_fetch should use to svn-test, not hg-test

* Drop Python 3 support in Mercurial

Python 3 support is a work in progress and isn't currently
recommended:

https://www.mercurial-scm.org/wiki/SupportedPythonVersions

* Test both secure and insecure hg fetching

* Test both secure and insecure git and svn fetching

var/spack/repos/builtin/packages/py-docutils/package.py

@@ -33,8 +33,18 @@ class PyDocutils(PythonPackage):
     markup language."""
 
     homepage = "http://docutils.sourceforge.net/"
-    url      = "https://pypi.python.org/packages/source/d/docutils/docutils-0.12.tar.gz"
+    url      = "https://pypi.io/packages/source/d/docutils/docutils-0.13.1.tar.gz"
 
-    version('0.13.1', 'ea4a893c633c788be9b8078b6b305d53',
-            url="https://pypi.python.org/packages/05/25/7b5484aca5d46915493f1fd4ecb63c38c333bd32aa9ad6e19da8d08895ae/docutils-0.13.1.tar.gz")
+    import_modules = [
+        'docutils', 'docutils.languages', 'docutils.parsers',
+        'docutils.readers', 'docutils.transforms', 'docutils.utils',
+        'docutils.writers', 'docutils.parsers.rst',
+        'docutils.parsers.rst.directives', 'docutils.parsers.rst.languages',
+        'docutils.utils.math', 'docutils.writers.html4css1',
+        'docutils.writers.html5_polyglot', 'docutils.writers.latex2e',
+        'docutils.writers.odf_odt', 'docutils.writers.pep_html',
+        'docutils.writers.s5_html', 'docutils.writers.xetex'
+    ]
+
+    version('0.13.1', 'ea4a893c633c788be9b8078b6b305d53')
     version('0.12',   '4622263b62c5c771c03502afa3157768')