Traceback (most recent call last):
  File "/usr/lib/python3.9/runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.9/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/home/mrichez/Workspace/tryton/6.0/.venv/trytond/lib/python3.9/site-packages/trytond/tests/run-tests.py", line 45, in <module>
    from trytond.tests.test_tryton import all_suite, modules_suite  # noqa: E402
  File "/home/mrichez/Workspace/tryton/6.0/.venv/trytond/lib/python3.9/site-packages/trytond/tests/test_tryton.py", line 41, in <module>
    Pool.start()
  File "/home/mrichez/Workspace/tryton/6.0/.venv/trytond/lib/python3.9/site-packages/trytond/pool.py", line 105, in start
    register_classes()
  File "/home/mrichez/Workspace/tryton/6.0/.venv/trytond/lib/python3.9/site-packages/trytond/modules/__init__.py", line 347, in register_classes
    the_module = import_module(module)
  File "/home/mrichez/Workspace/tryton/6.0/.venv/trytond/lib/python3.9/site-packages/trytond/modules/__init__.py", line 76, in import_module
    module = spec.loader.load_module()
  File "/home/mrichez/Workspace/tryton/6.0/preciball/__init__.py", line 7, in <module>
    from . import stock
  File "/home/mrichez/Workspace/tryton/6.0/preciball/stock/__init__.py", line 8, in <module>
    from . import stock
  File "/home/mrichez/Workspace/tryton/6.0/preciball/stock/stock.py", line 219, in <module>
    class PrintShippingLabelAskDetails(ModelView):
  File "/home/mrichez/Workspace/tryton/6.0/preciball/stock/stock.py", line 233, in PrintShippingLabelAskDetails
    'invisible': ~Eval('fields_required').contains(['customer', ])
  File "/home/mrichez/Workspace/tryton/6.0/.venv/trytond/lib/python3.9/site-packages/trytond/pyson.py", line 82, in contains
    return In(k, self)
  File "/home/mrichez/Workspace/tryton/6.0/.venv/trytond/lib/python3.9/site-packages/trytond/pyson.py", line 482, in __init__
    assert isinstance(key, (str, int)), \
AssertionError: key must be a string or an integer or a long