False positive with useless-super-delegation for required keyword args

[nicktimko]

False positive for useless-super-delegation for required keyword arguments. Subtle difference from #2006, a corner-case where #1618 fixing #1085 wasn't quite complete.

Steps to reproduce

# uselesssuper.py
class MyBase:
    def method(self, *, arg):
        self.x = arg

class MyChild(MyBase):
    def method(self, *, arg="I have value!"):
        super().method(arg=arg)

myobj = MyChild()
myobj.method()
print(myobj.x)

Current behavior

$ pylint --version
Using config file .../.pylintrc
pylint 1.8.4, 
astroid 1.6.3
Python 3.6.4 (default, Mar 26 2018, 16:21:07) 
[GCC 5.4.0 20160609]

$ python uselesssuper.py
I have value!

$ pylint uselesssuper.py --disable=all --enable=useless-super-delegation
Using config file .../.pylintrc
************* Module uselesssuper
W:  7, 4: Useless super delegation in method 'method' (useless-super-delegation)

------------------------------------------------------------------
Your code has been rated at 8.89/10 (previous run: 1.11/10, +7.78)

Expected behavior

No issue.

[PCManticore]

Thanks, makes sense!