tests: add tons of b prefixes in test-devel-warnings.t # skip-blame because it's just b prefixes Differential Revision: https://phab.mercurial-scm.org/D2207

py3: convert traceback representation to bytes when logging Python's APIs should return a system string. We want to use bytes for logging. So convert the traceback to bytes before sending it to the logger. Differential Revision: https://phab.mercurial-scm.org/D2176