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_pty.py b/Lib/test/test_pty.py
index 5551cd1..295ff3c 100644
--- a/Lib/test/test_pty.py
+++ b/Lib/test/test_pty.py
@@ -1,5 +1,5 @@
 import pty, os, sys, string
-from test_support import verbose, TestFailed
+from test_support import verbose, TestFailed, TestSkipped
 
 TEST_STRING_1 = "I wish to buy a fish license."
 TEST_STRING_2 = "For my pet fish, Eric."
@@ -25,7 +25,7 @@
     debug("Got slave_fd '%d'"%slave_fd)
 except OSError:
     # " An optional feature could not be imported " ... ?
-    raise ImportError, "Pseudo-terminals (seemingly) not functional."
+    raise TestSkipped, "Pseudo-terminals (seemingly) not functional."
 
 if not os.isatty(master_fd):
     raise TestFailed, "master_fd is not a tty"