Seems this is not reproducible at least on Python 3.6.4 and Master branch.

# bpo24997.py

from unittest.mock import *

m = Mock()
m(1,2)
m.call_args
print("1 ", m.call_args == call(1,2))
print("2 ", m.call_args != call(1,2))


# Master

./python.exe
Python 3.8.0a0 (heads/master:c510c6b8b6, Sep 21 2018, 11:10:24)
[Clang 7.0.2 (clang-700.1.81)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>
./python.exe ../backups/bpo24997.py
1  True
2  False

# Python 3.6.4

python3.6 ../backups/bpo24997.py
1  True
2  False


Thanks