gpg: use 'wvfs' instead of 'wfile' Method is about to be deprecated and the modern form is shorter.

test: add a basic 'test-check-pylint.t' We add a minimal check using pylint for one case we knows we care about: "mutable default" argument. We'll likely extend this over time to cover other useful checks but this is a good starting point.

localrepo: don't use mutable default argument value Caught by pylint.