#20903: clarify what happens when an smtp connection timeout occurs.

Patch by Milan Oberkirch.

Doc/library/smtplib.rst

@@ -32,7 +32,8 @@ Protocol) and :rfc:`1869` (SMTP Service Extensions).
    than a success code, an :exc:`SMTPConnectError` is raised. The optional
    *timeout* parameter specifies a timeout in seconds for blocking operations
    like the connection attempt (if not specified, the global default timeout
-   setting will be used). The optional source_address parameter allows to bind
+   setting will be used).  If the timeout expires, :exc:`socket.timeout` is
+   raised.  The optional source_address parameter allows to bind
    to some specific source address in a machine with multiple network
    interfaces, and/or to some specific source TCP port. It takes a 2-tuple
    (host, port), for the socket to bind to as its source address before