py3: use pycompat.bytestr to convert _b85chars to bytes The tranformer does append b'' to the value and make that a bytes but bytes in Python 3 returns the ascii value on getting characters using indexing. Characters of this string are queried using indexing multiple times in the file and to support that we use pycompat.bytestr which returns the bytechrs using indexing. Differential Revision: https://phab.mercurial-scm.org/D2072

py3: use pycompat.bytechr instead of chr Differential Revision: https://phab.mercurial-scm.org/D2071

py3: use pycompat.ziplist instead of zip zip returns a zip object instead of a list on Python 3. Differential Revision: https://phab.mercurial-scm.org/D2070