After writting python metro --selftest the following error message is produced metro_util.py:15: RuntimeWarning: Python C API version mismatch for module arrayfns: This Python has API version 1011, module arrayfns has version 1012. import arrayfns metro_util.py:15: RuntimeWarning: Python C API version mismatch for module _numpy: This Python has API version 1011, module _numpy has version 1012. import arrayfnsTraceback (most recent call last): File "metro", line 14, in ? import metro_logger File "metro_logger.py", line 6, in ? import metro_config File "metro_config.py", line 5, in ? import metro_config_validation File "metro_config_validation.py", line 8, in ? import metro_date File "metro_date.py", line 7, in ? import W3CDate ImportError: No module named W3CDate