dispatch: unify handler of IOError and OSError These exceptions were merged in Python 3.

dispatch: quote filename in IOError as well It's explicitly added for OSError at 720308f741cb "dispatch: show empty filename in OSError aborts". Let's do the same for IOError.

dispatch: add inline comment about possible IOError subtypes It's hard to tell which "if" would handle which exception.

convert: print exception message directly Otherwise the default repr() implementation will b'' prefix the returned str on Python 3. Differential Revision: https://phab.mercurial-scm.org/D5729

crecord: always return a str from uihunk.__repr__ Otherwise Python 3 complains about it returning bytes. Differential Revision: https://phab.mercurial-scm.org/D5728

tests: handles bytes/str mismatch in test-commit-interface-curses.t This fixes various test failures on Python 3. Differential Revision: https://phab.mercurial-scm.org/D5727

githelp: format with %d if an integer Python 3 doesn't allow us to format an int with %s like Python 2 did. So handle that. Differential Revision: https://phab.mercurial-scm.org/D5726

githelp: make argument parsing more compatible with Python 3 There were various mixing of str and bytes in here. This change fixes most of the failures in test-githelp.t. Differential Revision: https://phab.mercurial-scm.org/D5725

tests: add b'' prefixes to flagprocessorext.py Otherwise a part of test-flavprocessor.t fails due to not setting the proper key. Differential Revision: https://phab.mercurial-scm.org/D5724

tests: add b'' to config file name Without this, things die in the bowels of the config system due to mixing str and bytes. # skip-blame: just b'' prefix Differential Revision: https://phab.mercurial-scm.org/D5723