It is not a bug. Tuple is a callable, but calling it raises a TypeError with the informative error message.

It does not differ from e.g.

>>> def foo():
...     raise TypeError("don't call foo()")
... 
>>> callable(foo)
True
>>> foo()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in foo
TypeError: don't call foo()