Playing with the generalized unpacking (PEP 448), I found a funny error message, when duplicate dictionary unpackings are included and also duplicate a literal keyword argument:

>>> print(end=".\n", **dict(end="dupe"))  # No problem
TypeError: print() got multiple values for keyword argument 'end'
>>> print(**dict(end=".\n"), **dict(end="dupe"))  # No problem
TypeError: print() got multiple values for keyword argument 'end'
>>> print(end=".\n", **dict(end="dupe"), **dict(end="dupe 2"))  # str object?!
TypeError: str object got multiple values for keyword argument 'end'