diff -r c35d65c9ded3 Lib/test/test___all__.py
--- a/Lib/test/test___all__.py	Fri Nov 20 09:24:02 2015 +0100
+++ b/Lib/test/test___all__.py	Sun Nov 22 11:48:29 2015 +0100
@@ -1,6 +1,7 @@
 import unittest
 from test import support
 import os
+import re
 import sys
 
 
@@ -99,8 +100,9 @@
             try:
                 # This heuristic speeds up the process by removing, de facto,
                 # most test modules (and avoiding the auto-executing ones).
+
                 with open(path, "rb") as f:
-                    if b"__all__" not in f.read():
+                    if re.search(br'\b__all__\b', f.read()) is None:
                         raise NoAll(modname)
                     self.check_all(modname)
             except NoAll: