typing: make minor adjustments to mercurial/util.py to pass pytype checking
I'm assuming the wrong-arg-count is a pytype bug, because this code is used by
the config object. Avoiding initializing `_lrucachenode` node points to None
eliminates a few `is not None` assertions, but apparently not all of them. I
can't figure out why it gets confused over the state where these new assertions
are.
Differential Revision: https://phab.mercurial-scm.org/D10276
# rhg
This project provides a fastpath Rust implementation of the Mercurial (`hg`)
version control tool.