Tested with Python 3.10.1 on Linux and Python 3.10.0 on Windows.

The following code prints None in 3.9 and raises StopIteration without any additional information in 3.10:

    def f():
        yield
    
    x = f()
    
    try:
        x.send(0)
    except TypeError as e:
        print(e) # can't send non-None value to a just-started generator
    
    print(next(x))