Error when converting docx-files

[karatekaneen]

Steps to reproduce and/or test case demonstrating the problem

In the latest release in a docker environment we created a SIP with a single docx document as content.

Expected behavior

The file would be converted into format favorable for archiving.

Actual behavior

Got exception, full output:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/celery/app/trace.py", line 385, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/code/ESSArch_Core/WorkflowEngine/dbtask.py", line 93, in __call__
    return self._run(*args, **kwargs)
  File "/code/ESSArch_Core/WorkflowEngine/dbtask.py", line 115, in _run
    r = self._run_task(*args, **kwargs)
  File "/code/ESSArch_Core/WorkflowEngine/dbtask.py", line 131, in _run_task
    res = self.run(*args, **kwargs)
  File "/code/ESSArch_Core/tasks.py", line 829, in run
    convert_file(filepath, new_format)
  File "/code/ESSArch_Core/util.py", line 503, in convert_file
    raise ValueError(msg)
ValueError: b"unoconv: Cannot find a suitable pyuno library and python binary combination in /usr/lib/libreoffice\nERROR: No module named 'uno'\n\nunoconv: Cannot find a suitable office installation on your system.\nERROR: Please locate your office installation and send your feedback to:\n       http://github.com/dagwieers/unoconv/issues\n", return code: 1