ArgumentError: invalid option(s): known_hosts with net-ssh 3.0.2

[mattbrictson]

I saw this reported on Stack Overflow, and it seems like a legitimate bug introduced in sshkit 1.11.0.

https://stackoverflow.com/questions/37865299/capistrano-error-invalid-optionss-known-hosts

To summarize: starting with sshkit 1.11.0, we now pass a :known_hosts option to net-ssh by default (see #339). Unfortunately it seems that not all versions of net-ssh allow this. And instead of ignoring the option, net-ssh raises this error, at least in net-ssh 3.0.2:

ArgumentError: invalid option(s): known_hosts

The solution seems to be to upgrade to net-ssh 3.1.1.

@byroot Does this bug report seem legitimate? What can we do to fix this issue (other than change our gemspec to require newer net-ssh, which seems drastic)?

[casperisfine]

Hum, good point. I think we could check Net::SSH::VALID_OPTIONS, I'll PR something. https://github.com/net-ssh/net-ssh/blob/e884efe99fefe66eaddbd17b42b16c8112c6b9c5/lib/net/ssh.rb#L63