sudo add-apt-repository ppa:tiheum/equinox

More info: https://launchpad.net/~tiheum/+archive/ubuntu/equinox
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keybox '/tmp/tmp23af23ey/pubring.gpg' created
gpg: /tmp/tmp23af23ey/trustdb.gpg: trustdb created
gpg: key 464AD83D4631BBEA: public key "Launchpad equinoxart" imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg: no valid OpenPGP data found.
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.5/threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 688, in addkey_func
    func(**kwargs)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 386, in add_key
    return apsk.add_ppa_signing_key()
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 273, in add_ppa_signing_key
    cleanup(tmp_keyring_dir)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 234, in cleanup
    shutil.rmtree(tmp_keyring_dir)
  File "/usr/lib/python3.5/shutil.py", line 480, in rmtree
    _rmtree_safe_fd(fd, path, onerror)
  File "/usr/lib/python3.5/shutil.py", line 438, in _rmtree_safe_fd
    onerror(os.unlink, fullname, sys.exc_info())
  File "/usr/lib/python3.5/shutil.py", line 436, in _rmtree_safe_fd
    os.unlink(name, dir_fd=topfd)
FileNotFoundError: [Errno 2] 没有那个文件或目录: 'S.gpg-agent.browser'


请问这个问题是什么原因引起的，以及如何处理