remove system exits from datafetcher tests

apps/cli/executables/datafetcher/datafetcher/datafetcher.py

apps/cli/executables/datafetcher/datafetcher/errors.py

...i/executables/datafetcher/datafetcher/locations_report.py

...li/executables/datafetcher/datafetcher/project_fetcher.py

apps/cli/executables/datafetcher/datafetcher/return_codes.py

apps/cli/executables/datafetcher/datafetcher/utilities.py

apps/cli/executables/datafetcher/test/df_pytest_arg_utils.py

apps/cli/executables/datafetcher/test/df_pytest_utils.py

apps/cli/executables/datafetcher/test/df_testdata_utils.py

apps/cli/executables/datafetcher/test/mock_data_fetcher.py

apps/cli/executables/datafetcher/test/test_df_function.py

.../cli/executables/datafetcher/test/test_df_return_codes.py