Calibre crashing on start-up

Question

When I try to launch calibre I get the following error:

calibre
qt5ct: using qt5ct plugin
Gtk-Message: 14:55:04.251: Failed to load module "atk-bridge"
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'

I have executed sudo apt-get install libatk-adaptor:i386 libgail-common:i386 but the error remains the same.

lsb_release -a
LSB Version:    core-11.1.0ubuntu2-noarch:printing-11.1.0ubuntu2-noarch:security-11.1.0ubuntu2-noarch
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.1 LTS
Release:    20.04
Codename:   focal
/usr/bin/calibre --version
calibre (calibre 4.99.4)

Suggestions?

Answer 1

According to this link, it is a bug of Calibre.

To solve it, as suggested there, you have to replace line 110 (self._listener._unlink.cancel()) of /usr/lib/calibre/calibre/utils/ipc/server.py with the following content:

if self._listener._unlink is not None:
    self._listener._unlink.cancel()

Alternative solutions are to upgrade Calibre to 4.15 (or newer) or downgrade your python3 installation to a version prior to 3.8.3.