無法添加 snappy-dev/tools ppa 儲存庫

當我嘗試使用以下命令添加 snappy-dev/tools 儲存庫時，我正在使用 Deepin Linux 15.4.1 並且我想安裝包 snapcraft（為此我需要“標題的儲存庫”）：

sudo add-apt-repository ppa:snappy-dev/tools

但我得到了錯誤：

Official PPA for the Snappy related tools.
 More info: https://launchpad.net/~snappy-dev/+archive/ubuntu/tools
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keybox '/tmp/tmp4dbu3qkt/pubring.gpg' created
gpg: /tmp/tmp4dbu3qkt/trustdb.gpg: trustdb created
gpg: key F1831DDAFC42E99D: public key "Launchpad PPA for Snappy Developers" imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg: no valid OpenPGP data found.

當我第二次嘗試添加儲存庫時，我得到：

Snappy 相關工具的官方 PPA。更多資訊：https ://launchpad.net/~snappy-dev/+archive/ubuntu/tools Press

$$ ENTER $$繼續或 ctrl-c 取消添加它

gpg: keybox '/tmp/tmphwxyr_qo/pubring.gpg' created
gpg: /tmp/tmphwxyr_qo/trustdb.gpg: trustdb created
gpg: key F1831DDAFC42E99D: public key "Launchpad PPA for Snappy Developers" 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] Arquivo ou diretório não encontrado: 'S.gpg-agent.extra'

我在論壇上閱讀了很多關於這些東西的建議，但我沒有找到任何與我的錯誤相同的文章。我嘗試添加其他與 snap 相關的儲存庫，但我得到了與我在這篇文章中所說的相同的錯誤；我該如何解決這個問題？

評論中的答案：

snap install --candidate --classic snapcraft

引用自：https://unix.stackexchange.com/questions/396910