util: wrap s.encode('string_escape') call for future py3 compatibility

py3: prove hg tip works

py3: call strftime() with native str type Since strftime() may contain non-ascii character if locale set, we use strfrom/tolocal(). Now "hg tip" works.

encoding: add converter between native str and byte string This kind of encoding conversion is unavoidable on Python 3.

encoding: factor out unicode variants of from/tolocal() Unfortunately, these functions will be commonly used on Python 3.

py3: use next() to obtain next item from inner generator of generatorset .next attribute does not exist on Python 3. As this function seems to really care about the overhead of the Python interpreter, I follow the way of micro optimization.

py3: rewrite itervalues() as values() by importer I'm not a great fan of these importer magics, but this should be okay since "itervalues" seems as unique name as "iteritems".

py3: use portable way to stringify cache key of repoview

exewrapper: prefer HackableMercurial python if availbale Currently hg.exe will only try to load python27.dll from hg-python subdir if PYTHONHOME environment variable is not set. I think that it is better to check whether 'hg-python' subdir exists and load python from it in that case, regardless of environment. This allows for reliable approach of distributing Mercurial with its own Python.

import-checkers: split tests of the tool from running it on the source We did such splits for other tools already. The 'test-check-*.t' performs the check of the source code while the regular tests verifies the tools works. One of the benefit is that is provides a simple file to reuse in third party extensions.

py3: use bytestr wrapper in revsetlang.tokenize() This backs out 77270ec0cdd9 and wraps program by bytestr() instead.

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