Load custom environment setup from a Python source file and run the setup
    function.

def setup_custom_environment(custom_module_path):
    """Load custom environment setup from a Python source file and run the setup
    function.
    """
    module = import_file("maskrcnn_benchmark.utils.env.custom_module", custom_module_path)
    assert hasattr(module, "setup_environment") and callable(
        module.setup_environment
    ), (
        "Custom environment module defined in {} does not have the "
        "required callable attribute 'setup_environment'."
    ).format(
        custom_module_path
    )
    module.setup_environment()