Comment 0 for bug 1899035

from syslog:
Oct 8 16:24:07 mirian-pc systemd[1754]: Started Application launched by gnome-shell.
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: Traceback (most recent call last):
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: File "/usr/bin/calibre", line 20, in <module>
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: sys.exit(calibre())
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: File "/usr/lib/calibre/calibre/gui_launch.py", line 73, in calibre
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: main(args)
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: File "/usr/lib/calibre/calibre/gui2/main.py", line 543, in main
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: listener = create_listener()
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: File "/usr/lib/calibre/calibre/gui2/main.py", line 514, in create_listener
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: return Listener(address=gui_socket_address())
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: File "/usr/lib/calibre/calibre/utils/ipc/server.py", line 110, in __init__
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: self._listener._unlink.cancel()
Oct 8 16:24:07 mirian-pc calibre-gui.desktop[299116]: AttributeError: 'NoneType' object has no attribute 'cancel'
Oct 8 16:24:07 mirian-pc systemd[1754]: gnome-launched-calibre-gui.desktop-299116.scope: Succeeded.

in terminal:
$ /usr/bin/calibre
Traceback (most recent call last):
  File "/usr/bin/calibre", line 20, in <module>
    sys.exit(calibre())
  File "/usr/lib/calibre/calibre/gui_launch.py", line 73, in calibre
    main(args)
  File "/usr/lib/calibre/calibre/gui2/main.py", line 543, in main
    listener = create_listener()
  File "/usr/lib/calibre/calibre/gui2/main.py", line 514, in create_listener
    return Listener(address=gui_socket_address())
  File "/usr/lib/calibre/calibre/utils/ipc/server.py", line 110, in __init__
    self._listener._unlink.cancel()
AttributeError: 'NoneType' object has no attribute 'cancel'

calibre version:
4.99.4+dfsg+really4.12.0-1build1
ubuntu-focal-universe

ubuntu:
$ uname -a
Linux linux-pc 5.4.0-48-generic #52-Ubuntu SMP Thu Sep 10 10:58:49 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

$ python --version
Python 3.8.5