Traceback (most recent call last):
  File "tests/qapi-schema/test-qapi.py", line 56, in <module>
    schema = QAPISchema(sys.argv[1])
  File "scripts/qapi.py", line 1487, in __init__
    self.exprs = check_exprs(parser.exprs)
  File "scripts/qapi.py", line 921, in check_exprs
    check_union(expr, info)
  File "scripts/qapi.py", line 738, in check_union
    assert base_members
AssertionError