Replace list of constants with tuples of constants.
diff --git a/Lib/cgitb.py b/Lib/cgitb.py
index db46b25..735683e 100644
--- a/Lib/cgitb.py
+++ b/Lib/cgitb.py
@@ -146,7 +146,7 @@
             if name in done: continue
             done[name] = 1
             if value is not __UNDEF__:
-                if where in ['global', 'builtin']:
+                if where in ('global', 'builtin'):
                     name = ('<em>%s</em> ' % where) + strong(name)
                 elif where == 'local':
                     name = strong(name)