import py


def custom_file_error_formatter(item, results, errors):
    """Include the file path before each reported error."""
    return '\n'.join(
        '{path}:{error}'.format(
            path=py.path.local('.').bestrelpath(item.fspath),
            error=error,
        )   
        for error in errors
    )


def pytest_configure(config):
    plugin = config.pluginmanager.getplugin('mypy')
    plugin.file_error_formatter = custom_file_error_formatter