def checkUniqueness(some_list):
    """
    Verifies that every entry in a list is unique.  If it is not, it returns
    non-unique values.
    """

    unique_list = dict([(x,[]) for x in some_list]).keys()
    repeated_entries = [u for u in unique_list 
                        if len([s for s in some_list if s == u]) > 1]

    return repeated_entries