import module using file path

def _import_module(file_path):
    if not os.path.exists(file_path):
        raise ImportError

    module_name = os.path.splitext(os.path.basename(file_path))[0]
    module_dir = os.path.dirname(file_path)

    # Ugly inconsistency: Python will insist on correctly cased module names
    # independent of whether the OS is case-sensitive or not.
    # We want all cases to match though.
    if platform.system() == 'Windows':  # pragma: nocover
        for cased_file_path in os.listdir(module_dir):
            cased_module_name = os.path.splitext(cased_file_path)[0]
            if cased_module_name.lower() == module_name.lower():
                module_name = cased_module_name
                break

    if sys.version_info < (3, 5):
        from importlib.machinery import SourceFileLoader
        module = SourceFileLoader(module_name, file_path).load_module()
    else:
        import importlib.util
        spec = importlib.util.spec_from_file_location(module_name, file_path)
        module = importlib.util.module_from_spec(spec)
        spec.loader.exec_module(module)

    return module