This is likely related or a dupe of https://bugs.python.org/issue29270, but the error message is different.  I'm posting this to confirm it's the same issue, or not, and to at least provide a google result for people who also see this error as 29270 seems to imply this might not be fixable.

Like 29270, it involves the fact that the interpreter seems to be looking at my super() call inside of a method without actually calling it, and then getting upset about __classcell__:



from typing import NamedTuple


class X(NamedTuple):
    a: str
    b: str

    # comment this out to remove the issue
    def foo(self):
        return super(X, self)


and that's it!  on my interpreter:

Python 3.8.3 (default, May 23 2020, 16:34:37) 
[GCC 9.3.1 20200408 (Red Hat 9.3.1-2)] on linux

I get:

$ python test3.py 
Traceback (most recent call last):
  File "test3.py", line 4, in <module>
    class X(NamedTuple):
RuntimeError: __class__ not set defining 'X' as <class '__main__.X'>. Was __classcell__ propagated to type.__new__?

The most surprising thing is that this seems extremely basic and google is not finding this error message for me.