Improve the error message when the name template is wrong in `@cases_generator`

[smarie]

As of today the exception can be tricky to understand :)

(...)
..\..\..\..\..\_Libs_OpenSource\python-pytest-cases\pytest_cases\main_params.py:279: in get_all_cases
    for m in module:
E   TypeError: 'object' object is not iterable

During handling of the above exception, another exception occurred:
(...)
C:\Miniconda3\envs\baseenv\lib\site-packages\decopatch\utils_modes.py:132: in _apply_decorator
    return user_provided_applier(*new_args, **kwargs)
..\..\..\..\..\_Libs_OpenSource\python-pytest-cases\pytest_cases\main_params.py:210: in cases_data
    _cases = get_all_cases(cases, module, test_func, has_tag, filter)
..\..\..\..\..\_Libs_OpenSource\python-pytest-cases\pytest_cases\main_params.py:285: in get_all_cases
    _cases = extract_cases_from_module(m, has_tag=has_tag, filter=filter)
..\..\..\..\..\_Libs_OpenSource\python-pytest-cases\pytest_cases\main_params.py:344: in extract_cases_from_module
    _get_case_getter_s(f, code, cases_dct)
..\..\..\..\..\_Libs_OpenSource\python-pytest-cases\pytest_cases\main_params.py:398: in _get_case_getter_s
    gen_case_name = names(**gen_case_params_dct)
..\..\..\..\..\_Libs_OpenSource\python-pytest-cases\pytest_cases\main_params.py:384: in names
    return _formatter.format(**params)
E   IndexError: tuple index out of range