Add python version requirements to setup.py

This is need in the future so we can gracefully remove python 2.7 support.
See #1075.

Author: Blendify

docs/installing.rst

@@ -49,6 +49,14 @@ Symlink or subtree the ``sphinx_rtd_theme/sphinx_rtd_theme`` repository into you
 Compatibility
 =============
 
+Python
+------
+
+``sphinx_rtd_theme`` requires Python 2.7 or Python 3.4 or greater.
+
+Sphinx
+------
+
 ``sphinx_rtd_theme`` depends on at least Sphinx 1.6 although,
 we recommend at least Sphinx 2 to take advantage of the html5 writer.
 The html4 writer is still supported however,

setup.py

@@ -106,7 +106,7 @@ def run(self):
         'theme.conf',
         '*.html',
         'static/css/*.css',
-        'static/css/fonts/*.*'
+        'static/css/fonts/*.*',
         'static/js/*.js',
     ]},
     include_package_data=True,
@@ -116,8 +116,9 @@ def run(self):
             'sphinx_rtd_theme = sphinx_rtd_theme',
         ]
     },
+    python_requires='>=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*',
     install_requires=[
-        'sphinx>=1.6'
+        'sphinx>=1.6',
     ],
     tests_require=[
         'pytest',