Return the first installed font family in family list

def get_family(families):
    """Return the first installed font family in family list"""
    if not isinstance(families, list):
        families = [ families ]
    for family in families:
        if font_is_installed(family):
            return family
    else:
        print("Warning: None of the following fonts is installed: %r" % families)  # spyder: test-skip
        return QFont().family()