Rename function and add nice docstring.

--HG--
branch : pytest-2.7

setup.py

@@ -26,7 +26,18 @@ def get_version():
     raise ValueError("could not read version")
 
 
-def has_newish_setuptools():
+def has_environment_marker_support():
+    """
+    Tests that setuptools has support for PEP-426 environment marker support.
+    
+    The first known release to support it is 0.7 (and the earliest on PyPI seems to be 0.7.2 
+    so we're using that), see: http://pythonhosted.org/setuptools/history.html#id142
+    
+    References:
+    
+    * https://wheel.readthedocs.org/en/latest/index.html#defining-conditional-dependencies
+    * https://www.python.org/dev/peps/pep-0426/#environment-markers
+    """
     try:
         import setuptools
         import pkg_resources
@@ -39,7 +50,7 @@ def has_newish_setuptools():
 def main():
     install_requires = ['py>=1.4.25']
     extras_require = {}
-    if has_newish_setuptools():
+    if has_environment_marker_support():
         extras_require[':python_version=="2.6" or python_version=="3.0" or python_version=="3.1"'] = ['argparse']
         extras_require[':sys_platform=="win32"'] = ['colorama']
     else: