Return space available on remote device.

def remote_space_available(self, search_pattern=r"(\d+) bytes free"):
        """Return space available on remote device."""
        remote_cmd = 'system "df {}"'.format(self.folder_name)
        remote_output = self.ssh_ctl_chan.send_command_expect(remote_cmd)
        for line in remote_output.splitlines():
            if self.folder_name in line:
                space_available = line.split()[-3]
                break
        return int(space_available)