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