Fix pyflakes warnings: variable is assigned to but never used

[vstinner]

Example of fixed warning:

Lib/functools.py:690:21: local variable 'oldresult'
is assigned to but never used

[picnixz]

Wasn't this one important?

[vstinner]

Would you mind to elaborate? Important for what?

[picnixz]

There is the comment just above:

# Empty the oldest link and make it the new root.
# Keep a reference to the old key and old result to
# prevent their ref counts from going to zero during the
# update. That will prevent potentially arbitrary object
# clean-up code (i.e. __del__) from running while we're
# still adjusting the links.

which says that we want to keep a reference to the old result before doing the update. I would suggest using a noqa suppression to avoid hitting this one.