Show stream errors to user
Currently stream errors are not shown, and the user is informed that the connection failed, and they should check their connection.
A list of stream errors is at http://xmpp.org/internet-drafts/draft-saintandre-rfc3920bis-08.html#streams-error-conditions
An example might be host-unknown: "The server you are connecting to does not accept connections to 'example.com'. It may be misconfigured, or check that you have the correct address."
Also Gajim musn't make the mistake of other clients... you MUST show the <text> element of the error to the user if there is one :)