network.py hiding error, prompts for password

[SamuelMarks]

https://github.com/ploxiln/fab-classic/blob/ca674ab/fabric/network.py#L568

How about having a print(e) above that line?

[ploxiln]

Yeah, that sounds like a good idea.

One minor issue is that paramiko does not always raise the most appropriate error - it attempts a few different things, and then raises the last error, while the most relevant error was in the middle of the attempts. So we might just want to add some wording like "possible auth error: "