PEP 484: Clarify Python versioning in stub file search path (#410)

pep-0484.txt

@@ -1833,12 +1833,12 @@ they're updated often.
 
 Third-party stub packages can use any location for stub storage.  Type
 checkers should search for them using PYTHONPATH.  A default fallback
-directory that is always checked is ``shared/typehints/python3.5/`` (or
-3.6, etc.).  Since there can only be one package installed for a given
-Python version per environment, no additional versioning is performed
-under that directory (just like bare directory installs by ``pip`` in
-site-packages).  Stub file package authors might use the following
-snippet in ``setup.py``::
+directory that is always checked is ``shared/typehints/pythonX.Y/`` (for
+some PythonX.Y as determined by the type checker, not just the installed
+version).  Since there can only be one package installed for a given Python
+version per environment, no additional versioning is performed under that
+directory (just like bare directory installs by ``pip`` in site-packages).
+Stub file package authors might use the following snippet in ``setup.py``::
 
   ...
   data_files=[