Avoid PacketizerTest.test_closed_3 to fail on platforms where errno.E…

…TIME

is not defined

This changes define the proper Timer expired error message instead of raising
AttributeError when errno.ETIME is not available on the platform. fixes paramiko#862

tests/test_packetizer.py

@@ -114,9 +114,13 @@ def test_3_closed(self):
         import signal
 
         class TimeoutError(Exception):
-            pass
+            def __init__(self, error_message):
+                if hasattr(errno, 'ETIME'):
+                    self.message = os.sterror(errno.ETIME)
+                else:
+                    self.messaage = error_message
 
-        def timeout(seconds=1, error_message=os.strerror(errno.ETIME)):
+        def timeout(seconds=1, error_message='Timer expired'):
             def decorator(func):
                 def _handle_timeout(signum, frame):
                     raise TimeoutError(error_message)