I encountered a question on Stackoverflow where, unusually, a Traceback was given in full, but I couldn't diagnose the problem.

It was like this:

Traceback (most recent call last):
  File "soFailedTraceback.py", line 15, in <module>
    c = C(C1("C1"), C2("C2"))
TypeError: __init__() missing 1 required positional argument: 'p'

What I am claiming is missing is info about class C1:
  File "soFailedTraceback.py", line 8, in <module>
    def __init__(self, s1, p):


Here is the file soFailedTraceback.py:
#soFailedTraceback

class C:
    def __init__(self, c1, p):
        pass

class C1:
    def __init__(self, s1, p):
        pass

class C2:
    def __init__(self, s1):
        pass

c = C(C1("C1"), C2("C2"))

I find the Traceback confusing, because it so happens there are two classes which have required positional argument "p", but python does not directly show which class it is.