Raise 'TestSkipped' (from the test_support) module rather than 'ImportError'
to signify a test that should be marked as 'skipped' rather than 'failed'.
Also 'document' it, in README.
diff --git a/Lib/test/test_openpty.py b/Lib/test/test_openpty.py
index 1202845..723e57c 100644
--- a/Lib/test/test_openpty.py
+++ b/Lib/test/test_openpty.py
@@ -1,7 +1,7 @@
 # Test to see if openpty works. (But don't worry if it isn't available.)
 
 import os
-from test_support import verbose, TestFailed
+from test_support import verbose, TestFailed, TestSkipped
 
 try:
     if verbose:
@@ -10,7 +10,7 @@
     if verbose:
         print "(master, slave) = (%d, %d)"%(master, slave)
 except AttributeError:
-    raise ImportError, "No openpty() available."
+    raise TestSkipped, "No openpty() available."
 
 if not os.isatty(master):
     raise TestFailed, "Master-end of pty is not a terminal."