code: def perform_preflight_check(self):
          
          failures = []
          if not os.access(self.mount_path_base, os.W_OK):
              msg = ("Mount path `{path}` doesn't exist or is not writable"
                     " by the current user.")
              failures.append(msg.format(
                  path = self.mount_path_base
              ))
          if which('sshfs') is None:
              msg = ("SSHFS (http://fuse.sourceforge.net/sshfs.html)"
                     " does not seem to be installed.")
              failures.append(msg)
  
          return len(failures) == 0, failures
docs: Performs checks to see if we have everything needed to mount
          sshfs filesystems.
          :return: two-tuple (boolean checks_pass, list failure messages)