#2503 make singletons compared with "is" not == or !=
Thanks to Wummel for the patch
diff --git a/Lib/plat-os2emx/grp.py b/Lib/plat-os2emx/grp.py
index fceb4c9..a5f3468 100644
--- a/Lib/plat-os2emx/grp.py
+++ b/Lib/plat-os2emx/grp.py
@@ -143,7 +143,7 @@
     while 1:
         entry = group.readline().strip()
         if len(entry) > 3:
-            if sep == None:
+            if sep is None:
                 sep = __get_field_sep(entry)
             fields = entry.split(sep)
             fields[2] = int(fields[2])