Check if SSH is available on a host.

def is_ssh_available(host, opts, print_ssh_output=True):
    """
    Check if SSH is available on a host.
    """
    s = subprocess.Popen(
        ssh_command(opts) + ['-t', '-t', '-o', 'ConnectTimeout=3',
                             '%s@%s' % (opts.user, host), stringify_command('true')],
        stdout=subprocess.PIPE,
        stderr=subprocess.STDOUT  # we pipe stderr through stdout to preserve output order
    )
    cmd_output = s.communicate()[0]  # [1] is stderr, which we redirected to stdout

    if s.returncode != 0 and print_ssh_output:
        # extra leading newline is for spacing in wait_for_cluster_state()
        print(textwrap.dedent("""\n
            Warning: SSH connection error. (This could be temporary.)
            Host: {h}
            SSH return code: {r}
            SSH output: {o}
        """).format(
            h=host,
            r=s.returncode,
            o=cmd_output.strip()
        ))

    return s.returncode == 0