`test_cod_widget` not the most reliable test

[edan-bainglass]

Working on #647, I updated the main commit with a comment. All of a sudden, test_cod_widget was failing. I re-ran the failed test, only for it to fail again. @danielhollas re-ran it later - passed! Not reliable. @danielhollas note that I can't figure out how to paste the failure here, since your successful re-running of the test appears to have overwritten the failure. If you're aware of a way to recover it, please add it here.

[danielhollas]

The error was:

___________________________ test_cod_query_widget _____________________________

    @pytest.mark.timeout(30)
    def test_cod_query_widget():
        """Test the COD query widget."""
    
        widget = awb.CodQueryWidget()
    
        # Enter the query string.
        widget.inp_elements.value = "Ni Ti"
    
        # Run the query.
        widget._on_click_query()
    
        # Select one of the results.
        # TODO: Select a different structure to get rid of the ASE warning:
        # "ase/io/cif.py:401: UserWarning: crystal system 'cubic' is not interpreted
        # for space group 'Pm-3m'. This may result in wrong setting!"
>       widget.drop_structure.label = "NiTi (id: 1100132)"

tests/test_databases.py:25: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/opt/hostedtoolcache/Python/3.9.20/x64/lib/python3.9/site-packages/traitlets/traitlets.py:716: in __set__
    self.set(obj, value)
/opt/hostedtoolcache/Python/3.9.20/x64/lib/python3.9/site-packages/traitlets/traitlets.py:690: in set
    new_value = self._validate(obj, value)
/opt/hostedtoolcache/Python/3.9.20/x64/lib/python3.9/site-packages/traitlets/traitlets.py:724: in _validate
    value = self._cross_validate(obj, value)
/opt/hostedtoolcache/Python/3.9.20/x64/lib/python3.9/site-packages/traitlets/traitlets.py:730: in _cross_validate
    value = obj._trait_validators[self.name](obj, proposal)
/opt/hostedtoolcache/Python/3.9.20/x64/lib/python3.9/site-packages/traitlets/traitlets.py:1241: in __call__
    return self.func(*args, **kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = Dropdown(layout=Layout(width='400px'), options=(('select structure', {'status': False}),), style=DescriptionStyle(description_width='initial'), value={'status': False})
proposal = {'trait': <traitlets.traitlets.Unicode object at 0x7f512537bc70>, 'value': 'NiTi (id: 1100132)', 'owner': Dropdown(lay...select structure', {'status': False}),), style=DescriptionStyle(description_width='initial'), value={'status': False})}

    @validate('label')
    def _validate_label(self, proposal):
        if (proposal.value is not None) and (proposal.value not in self._options_labels):
>           raise TraitError('Invalid selection: label not found')
E           traitlets.traitlets.TraitError: Invalid selection: label not found

/opt/hostedtoolcache/Python/3.9.20/x64/lib/python3.9/site-packages/ipywidgets/widgets/widget_selection.py:259: TraitError

I can't figure out how to paste the failure here, since your successful re-running of the test appears to have overwritten the failure. If you're aware of a way to recover it, please add it here.

You can get to the logs from previous runs using the dropdown menu in top-right corner: