Function get_data_dir

fn get_data_dir(
    udf_env: &str,
    submodule_data: &str,
) -> Result<PathBuf, Box<dyn Error>>

Returns a directory path for finding test data.

udf_env: name of an environment variable

submodule_dir: fallback path (relative to CARGO_MANIFEST_DIR)

Returns either: The path referred to in udf_env if that variable is set and refers to a directory The submodule_data directory relative to CARGO_MANIFEST_PATH