Fixing observed timeout during JOSS review

[daavid00]

Description

This PR aims to fix the issue raised by @nasserma:

Traceback (most recent call last):
  File "/home/nasser/.local/bin/pycopm", line 8, in <module>
    sys.exit(main())
             ~~~~^^
  File "/home/nasser/.local/lib/python3.14/site-packages/pycopm/core/pycopm.py", line 454, in main
    pycopm()
    ~~~~~~^^
  File "/home/nasser/.local/lib/python3.14/site-packages/pycopm/core/pycopm.py", line 101, in pycopm
    process_input(dic, file)
    ~~~~~~~~~~~~~^^^^^^^^^^^
  File "/home/nasser/.local/lib/python3.14/site-packages/pycopm/utils/input_values.py", line 42, in process_input
    check_flow(dic, in_file)
    ~~~~~~~~~~^^^^^^^^^^^^^^
  File "/home/nasser/.local/lib/python3.14/site-packages/pycopm/utils/input_values.py", line 67, in check_flow
    flowtoml = subprocess.call(
        dic["flowpth"].strip(),
    ...<2 lines>...
        stdout=subprocess.DEVNULL,
    )
  File "/usr/lib/python3.14/subprocess.py", line 398, in call
    return p.wait(timeout=timeout)
           ~~~~~~^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.14/subprocess.py", line 1279, in wait
    return self._wait(timeout=timeout)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.14/subprocess.py", line 2084, in _wait
    (pid, sts) = self._try_wait(0)
                 ~~~~~~~~~~~~~~^^^
  File "/usr/lib/python3.14/subprocess.py", line 2042, in _try_wait
    (pid, sts) = os.waitpid(self.pid, wait_flags)
                 ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
KeyboardInterrupt

PR part os the JOSS review openjournals/joss-reviews#10124

[daavid00]

@nasserma, could you please check if flow was installed properly in your system by executing inside the pycopm repository:

flow examples/decks/HELLO_WORLD.DATA --output-dir=test_outputs

If this runs, then could you please check if this PR fixes the issue by trying to run:

pycopm -i examples/decks/HELLO_WORLD.DATA -o test_outputs -c 2,1,1

[daavid00]

Update: I have included in this PR to run the ci_pycopm_ubuntu.yml with ubuntu:26.04 and Python 3.14, and the Action has successfully passed https://github.com/cssr-tools/pycopm/actions/runs/27058251020