PEP 493: link to issue with the implementation

pep-0493.txt

@@ -256,6 +256,13 @@ works the same way regardless of whether or not the interpreter is being run
 inside an activated Python virtual environment.
 
 
+Reference Implementation
+========================
+
+A patch for Python 2.7 implementing the above two features is attached to
+the `relevant tracker issue <http://bugs.python.org/issue23857>`__.
+
+
 Backporting this PEP to earlier Python versions
 ===============================================