def get_pack_warnings(pack_metadata):
    """
    Return warning string if pack metadata indicates only python 2 is supported

    :rtype: ``str``
    """
    warning = None
    versions = pack_metadata.get("python_versions", None)
    pack_name = pack_metadata.get("name", None)
    if versions and set(versions) == set(["2"]):
        warning = PACK_PYTHON2_WARNING % pack_name
    return warning

    Return warning string if pack metadata indicates only python 2 is supported

    :rtype: ``str``
    
st2common/st2common/util/pack.py