Detects whether we have everything needed to mount sshfs filesystems.

def command_preflight_check(self):
        """Detects whether we have everything needed to mount sshfs filesystems.
        """
        checks_pass, failures = self.environment.perform_preflight_check()
        if checks_pass:
            print('All checks pass.')
        else:
            sys.stderr.write('Problems encountered:\n')
            for msg in failures:
                sys.stderr.write(' - %s\n' % msg)
            sys.exit(1)