exit with traceback when block device dissapears from os before being removed from targetcli

[mailinglists35]

steps to reproduce

create entry in /backstores/block

add it to a tpg

exit targetcli

in os do echo 1 > /sys/block/sdX/device/delete

return to targetcli

/> ls
Traceback (most recent call last):
  File "/usr/bin/targetcli", line 122, in <module>
    main()
  File "/usr/bin/targetcli", line 112, in main
    shell.run_interactive()
  File "/usr/lib/python3/dist-packages/configshell_fb/shell.py", line 905, in run_interactive
    self._cli_loop()
  File "/usr/lib/python3/dist-packages/configshell_fb/shell.py", line 734, in _cli_loop
    self.run_cmdline(cmdline)
  File "/usr/lib/python3/dist-packages/configshell_fb/shell.py", line 848, in run_cmdline
    self._execute_command(path, command, pparams, kparams)
  File "/usr/lib/python3/dist-packages/configshell_fb/shell.py", line 823, in _execute_command
    result = target.execute_command(command, pparams, kparams)
  File "/usr/lib/python3/dist-packages/configshell_fb/node.py", line 1406, in execute_command
    return method(*pparams, **kparams)
  File "/usr/lib/python3/dist-packages/configshell_fb/node.py", line 710, in ui_command_ls
    tree = self._render_tree(target, depth=depth)
  File "/usr/lib/python3/dist-packages/configshell_fb/node.py", line 861, in _render_tree
    + self._render_tree(children[i], margin, depth)
  File "/usr/lib/python3/dist-packages/configshell_fb/node.py", line 861, in _render_tree
    + self._render_tree(children[i], margin, depth)
  File "/usr/lib/python3/dist-packages/configshell_fb/node.py", line 861, in _render_tree
    + self._render_tree(children[i], margin, depth)
  File "/usr/lib/python3/dist-packages/configshell_fb/node.py", line 765, in _render_tree
    (description, is_healthy) = root.summary()
  File "/usr/lib/python3/dist-packages/targetcli/ui_backstore.py", line 749, in summary
    return ("%s (%s) %s%s %s" % (so.udev_path, bytes_to_human(so.size),
  File "/usr/lib/python3/dist-packages/rtslib_fb/tcm.py", line 748, in _get_size
    return get_size_for_disk_name(self._parse_info('device')) * int(self._parse_info('SectorSize'))
  File "/usr/lib/python3/dist-packages/rtslib_fb/utils.py", line 180, in get_size_for_disk_name
    return get_size(name)
  File "/usr/lib/python3/dist-packages/rtslib_fb/utils.py", line 171, in get_size
    device = pyudev.Device.from_name(_CONTEXT, 'block', name)
  File "/usr/lib/python3/dist-packages/pyudev/device/_device.py", line 414, in from_name
    return Devices.from_name(context, subsystem, sys_name)
  File "/usr/lib/python3/dist-packages/pyudev/device/_device.py", line 139, in from_name
    raise DeviceNotFoundByNameError(subsystem, sys_name)
pyudev.device._errors.DeviceNotFoundByNameError: No device 'sdc' in 'block'

you can fix if you remember the name by going again into /backstores/block and deleting
but if you don't remember the name, how do you find it to delete it if ls crashes?