agent broken test in Py 3.6: TestScriptRunner.test_script_runner_downloable

Hi. Building murano-agent 3.4.0 (aka: Queens release) in Debian Sid using Python 3.6 leads to the below stack dump. It looks like the test is broken (but I can't tell about the code...) since we're seeing a MagicMock object from unittest / mock.

FAIL: muranoagent.tests.unit.test_script_runner.TestScriptRunner.test_script_runner_downloable
muranoagent.tests.unit.test_script_runner.TestScriptRunner.test_script_runner_downloable
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_StringException: Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/mock/mock.py", line 1305, in patched
    return func(*args, **keywargs)
  File "/<<PKGBUILDDIR>>/muranoagent/tests/unit/test_script_runner.py", line 42, in test_script_runner_downloable
    scripts._prepare_files()
  File "/<<PKGBUILDDIR>>/muranoagent/script_runner.py", line 75, in _prepare_files
    return os.path.join(self._files_manager._cache_folder, self._name)
  File "/usr/lib/python3.6/posixpath.py", line 80, in join
    a = os.fspath(a)
TypeError: expected str, bytes or os.PathLike object, not MagicMock