Fail Fast for Certain Errors

[mariotaku]

Hi! I implemented a SSH connection pool in my project, and noticed when the connection can't be created (no route to host, failed to authenticate etc), get_timeout will actually retry until timeout.

I'd like to have an option to allow fail-fast for such case. In my fork, I added can_retry function in HandleError, and when it returns false, it will fail immediately without retry.

6ab3302...aaa2a2b

Do you think this feature makes sense? If so, I'll create a pull request.