This is all minor stuff: unreachable debug code (that should be commented-out
instead of in an 'if False:' block), unnecessary 'pass' and 'global'
statements, redundantly-initialized variables. No behavior changes. Nothing
here was actually broken, it just looked suspicious to the static analysis at
https://lgtm.com/projects/g/tahoe-lafs/tahoe-lafs/alerts/?mode=list .
