Jack Jansen reported that the regression test failed on the Mac where
string.letters was much more than expected.

Solution: explicit is better than implicit; don't rely on
string.letters.
diff --git a/Lib/test/test_StringIO.py b/Lib/test/test_StringIO.py
index f2d6dbf..b1fca84 100644
--- a/Lib/test/test_StringIO.py
+++ b/Lib/test/test_StringIO.py
@@ -1,9 +1,7 @@
 # Tests StringIO and cStringIO
 
-import string
-
 def do_test(module):
-    s = (string.letters+'\n')*5
+    s = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"+'\n')*5
     f = module.StringIO(s)
     print f.read(10)
     print f.readline()