py3: use bytestr wrapper in revsetlang.formatspec() This backs out 1c48a8278b2f and wraps expr by bytestr() instead.

pycompat: add bytestr wrapper which mostly acts as a Python 2 str This allows us to handle bytes in mostly the same manner as Python 2 str, so we can get rid of ugly s[i:i + 1] hacks: s = bytestr(s) while i < len(s): c = s[i] ... This is the simpler version of the previous RFC patch which tried to preserve the bytestr type if possible. New version simply drops the bytestr wrapping so we aren't likely to pass a bytestr to a function that expects Python 3 bytes.

tests: allow running doctests selectively on Python 3 Currently most doctests fail on Python 3, but I want to add some.

context: explicitly tests for None Changeset 9e57033fec0c removed the mutable default value, but did not explicitly tested for None. Such implicit testing can introduce semantic and performance issue. We move to an explicit testing for None as recommended by PEP8: https://www.python.org/dev/peps/pep-0008/#programming-recommendations

filemerge: explicitly tests for None Changeset 758526333dec removed the mutable default value, but did not explicitly tested for None. Such implicit testing can introduce semantic and performance issue. We move to an explicit testing for None as recommended by PEP8: https://www.python.org/dev/peps/pep-0008/#programming-recommendations

hgweb: explicitly tests for None Changeset 7dafa8d0e006 removed the mutable default value, but did not explicitly tested for None. Such implicit testing can introduce semantic and performance issue. We move to an explicit testing for None as recommended by PEP8: https://www.python.org/dev/peps/pep-0008/#programming-recommendations