FileNotFoundError

I appreciate the feedback, Mathilde.
I attempted to reproduce this issue, and unfortunately I can't see that error.

To be sure, it's a bug if it can't handle a relative path.
If you give it an absolute path to the preseed file, does that help?
In what directory are you running this? $HOME or something under it perhaps?
Anything else you can think of that might help to reproduce the issue?

Hi Dan, I'm facing a similar bug too. As recommended by you, I tried using the absolute path but that did not work. And I am running it under /home/<User> dir, The error I get -

Traceback (most recent call last):
  File "/snap/autoinstall-generator/64/usr/bin/autoinstall-generator", line 56, in <module>
    sys.exit(main())
  File "/snap/autoinstall-generator/64/usr/bin/autoinstall-generator", line 47, in main
    out = convert_file(infile, args)
  File "/snap/autoinstall-generator/64/lib/python3.6/site-packages/autoinstall_generator/merging.py", line 206, in convert_file
    directives.append(convert(line.strip('\n'), idx + 1))
  File "/snap/autoinstall-generator/64/lib/python3.6/site-packages/autoinstall_generator/convert.py", line 280, in convert
    return dispatch(line, pkg, key, value, linenumber)
  File "/snap/autoinstall-generator/64/lib/python3.6/site-packages/autoinstall_generator/convert.py", line 251, in dispatch
    return debconf_fragment(value, line, linenumber)
  File "/snap/autoinstall-generator/64/lib/python3.6/site-packages/autoinstall_generator/convert.py", line 163, in debconf_fragment
    key = f'{chunks[0]} {chunks[1]}'
IndexError: list index out of range

Have there been ANY testing on this app? Because it's just hilarious how it fails a basic thing:

root@netboot:~# stat /srv/pxe/ubuntu/20/chroot.preseed
  File: /srv/pxe/ubuntu/20/chroot.preseed
  Size: 3067 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 1580138 Links: 2
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2022-10-26 16:30:36.216674530 +0300
Modify: 2020-12-17 18:29:12.480162194 +0200
Change: 2020-12-17 18:29:12.480162194 +0200
 Birth: -

root@netboot:~# autoinstall-generator /srv/pxe/ubuntu/20/chroot.preseed /root/moo.file
Traceback (most recent call last):
  File "/snap/autoinstall-generator/104/usr/bin/autoinstall-generator", line 56, in <module>
    sys.exit(main())
  File "/snap/autoinstall-generator/104/usr/bin/autoinstall-generator", line 45, in main
    infile = open(args.inpath, 'r', encoding='utf-8')
FileNotFoundError: [Errno 2] No such file or directory: '/srv/pxe/ubuntu/20/chroot.preseed'

Just to be clear, the only way I was able to get this to work was to install it with pip3:

# pip3 install git+https://github.com/canonical/autoinstall-generator.git

Which then works as expected:

# /usr/local/bin/autoinstall-generator.py /srv/pxe/ubuntu/20/chroot.preseed /root/moo.file

But the snap is clearly not working due to some security confinements.