Retrieve CSV file with version information for reference data.

def _get_data_versions(data):
    """Retrieve CSV file with version information for reference data.
    """
    genome_dir = install.get_genome_dir(data["genome_build"], data["dirs"].get("galaxy"), data)
    if genome_dir:
        version_file = os.path.join(genome_dir, "versions.csv")
        if version_file and os.path.exists(version_file):
            return version_file
    return None