Enumerate available gemini data files in a standard installation.

def get_gemini_files(data):
    """Enumerate available gemini data files in a standard installation.
    """
    try:
        from gemini import annotations, config
    except ImportError:
        return {}
    return {"base": config.read_gemini_config()["annotation_dir"],
            "files": annotations.get_anno_files().values()}