Add helpers for testing unicode disabled builds.

Lib/test/test_support.py

@@ -498,13 +498,18 @@ PIPE_MAX_SIZE = 4 * 1024 * 1024 + 1
 # for a discussion of this number).
 SOCK_MAX_SIZE = 16 * 1024 * 1024 + 1
 
+is_jython = sys.platform.startswith('java')
+
 try:
     unicode
     have_unicode = True
 except NameError:
     have_unicode = False
 
-is_jython = sys.platform.startswith('java')
+requires_unicode = unittest.skipUnless(have_unicode, 'no unicode support')
+
+def u(s):
+    return unicode(s, 'unicode-escape')
 
 # FS_NONASCII: non-ASCII Unicode character encodable by
 # sys.getfilesystemencoding(), or None if there is no such character.