tests: port helper script revlog-formatv0.py to python 3 Differential Revision: https://phab.mercurial-scm.org/D2540

tests: add missing b prefix in test python in test-issue2137.t # skip-blame just a b prefix Differential Revision: https://phab.mercurial-scm.org/D2539

templatefilters: convert arguments to sysstrs for unicode() ctor Differential Revision: https://phab.mercurial-scm.org/D2538

py3: use util.forcebytestr() to convert IOErrors to bytes Differential Revision: https://phab.mercurial-scm.org/D2536

py3: whitelist three more passing tests Differential Revision: https://phab.mercurial-scm.org/D2530

convert: fix two %r output formats with pycompat.bytestr() wrapping Differential Revision: https://phab.mercurial-scm.org/D2529

convert: use our shlex wrapper in filemap to avoid Python 3 tracebacks Differential Revision: https://phab.mercurial-scm.org/D2527

convcmd: use our shlex wrapper to avoid Python 3 tracebacks Differential Revision: https://phab.mercurial-scm.org/D2526

convert: add some utility code for working with shlex on Python 3 This could have gone in pycompat, but it's only needed in convert, so I figured it made more sense here. It's got py3 in the name and checks pycompat.ispy3, so we'll find it whenever we decide to drop Python 2 support in 20x6. # no-check-commit because of required foo_bar naming on the proxy class Differential Revision: https://phab.mercurial-scm.org/D2525

pycompat: add support for encoding argument to our wrapper This only works on Python 3, but I'm about to need it for a regrettable hack in the convert code. Differential Revision: https://phab.mercurial-scm.org/D2524