NamedTuple subclasses are not considered callable even when they have a __call__ method

[msullivan]

from typing import Tuple, NamedTuple

Thing = NamedTuple('Thing', [('s', str), ('n', int)])

class CallableTuple(Thing):
    def __call__(self) -> str:
        return self.s + str(self.n)

o = CallableTuple('hello ', 12)
print(o())

produces the message
error: "CallableTuple" not callable

[ilevkivskyi]

This one is easy, just add another elif for TupleType in checkexpr.check_call that just calls check_call on tuple fallback