util: convert traceback-related sysstrs to sysbytes in getstackframes With this change, test-devel-warnings.t passes except for differences in how ProgrammingError is formatted and one mysterious traceback inside of transaction.__del__. Differential Revision: https://phab.mercurial-scm.org/D2212

util: format line number of stack trace using %d Required on Python 3, functional on Python 2. Differential Revision: https://phab.mercurial-scm.org/D2211

util: call warnings.warn() with a sysstr in nouideprecwarn This preserves nouideprecwarn wanting a bytes, which is consistent with the rest of hg. Differential Revision: https://phab.mercurial-scm.org/D2210

ui: convert stack traces to sysbytes before logging They're coming back as unicodes, so sysbytes seems like the best we can do. This is like D2171 and D2172, but those fail on Python 2.7.5 (seriously!), so this is my version of the same change. I actually wrote this before reviewing those, then discarded it, then came back to it after finding out 2.7.5 is a silly place. Differential Revision: https://phab.mercurial-scm.org/D2209

ui: use pycompat.bytestr() to get a bytes-repr of config default We don't know what type we'll get here, so we need something that'll behave like a repr without returning a unicode. Differential Revision: https://phab.mercurial-scm.org/D2208

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