def _debuginit(self, exc_value=None, exc_type=None, exc_tb=None,
               captureVars=False,
               Failure__init__=Failure.__init__):
    """
    Initialize failure object, possibly spawning pdb.
    """
    if (exc_value, exc_type, exc_tb) == (None, None, None):
        exc = sys.exc_info()
        if not exc[0] == self.__class__ and DO_POST_MORTEM:
            try:
                strrepr = str(exc[1])
            except:
                strrepr = "broken str"
            print("Jumping into debugger for post-mortem of exception '%s':" %
                  (strrepr,))
            import pdb
            pdb.post_mortem(exc[2])
    Failure__init__(self, exc_value, exc_type, exc_tb, captureVars)

    Initialize failure object, possibly spawning pdb.
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/failure.py