bpo-31681: Make sure pkgutil.get_data closes files properly (#3875)

Also remove an obsolete note about
backward compat with old Pythons.

Lib/pkgutil.py

 """Utilities to support packages."""
 
-# NOTE: This module must remain compatible with Python 2.3, as it is shared
-# by setuptools for distribution with Python 2.3 and up.
-
 import os
 import sys
 import imp
@@ -252,7 +249,8 @@ class ImpLoader:
         return mod
 
     def get_data(self, pathname):
-        return open(pathname, "rb").read()
+        with open(pathname, "rb") as file:
+            return file.read()
 
     def _reopen(self):
         if self.file and self.file.closed:

Misc/NEWS.d/next/Library/2017-10-03-15-41-08.bpo-31681.sOJMKV.rst

+Fix pkgutil.get_data to avoid leaking open files.