I tried to import an mbox using the command:

sudo ./manage.py hyperkitty_import -l korus@lists.xxx.hu /var/lib/mailman/archives/private/korus.mbox

I got the error message below, even if korus.mbox is a normal file (1.4GB large though). How can I import it without error?

Importing from mbox file /var/lib/mailman/archives/private/korus.mbox to korus@lists.xxx.hu Traceback (most recent call last): File "/usr/share/mailman3-web/./manage.py", line 10, in <module> execute_from_command_line(sys.argv) File "/usr/lib/python3/dist-packages/django/core/management/__init__.py", line 381, in execute_from_command_line utility.execute() File "/usr/lib/python3/dist-packages/django/core/management/__init__.py", line 375, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/usr/lib/python3/dist-packages/django/core/management/base.py", line 323, in run_from_argv self.execute(*args, **cmd_options) File "/usr/lib/python3/dist-packages/django/core/management/base.py", line 364, in execute output = self.handle(*args, **options) File "/usr/lib/python3/dist-packages/hyperkitty/management/commands/hyperkitty_import.py", line 355, in handle importer.from_mbox(mbfile, report_name) File "/usr/lib/python3/dist-packages/hyperkitty/management/commands/hyperkitty_import.py", line 149, in from_mbox mbox = mailbox.mbox(mbfile) File "/usr/lib/python3.9/mailbox.py", line 850, in __init__ _mboxMMDF.__init__(self, path, factory, create) File "/usr/lib/python3.9/mailbox.py", line 584, in __init__ f = open(self._path, 'rb+') IsADirectoryError: [Errno 21] Is a directory: '/var/lib/mailman/archives/private/korus.mbox'