Issue #16647: save socket error details in LMTP.connect()

Initial patch by Serhiy Storchaka.
diff --git a/Lib/test/test_smtplib.py b/Lib/test/test_smtplib.py
index befc49e..6fe2df9 100644
--- a/Lib/test/test_smtplib.py
+++ b/Lib/test/test_smtplib.py
@@ -542,9 +542,9 @@
 
     def testNonnumericPort(self):
         # check that non-numeric port raises socket.error
-        self.assertRaises(mock_socket.error, smtplib.SMTP,
+        self.assertRaises(OSError, smtplib.SMTP,
                           "localhost", "bogus")
-        self.assertRaises(mock_socket.error, smtplib.SMTP,
+        self.assertRaises(OSError, smtplib.SMTP,
                           "localhost:bogus")