parsers: handle refcounting of "parents" consistently Py_None can be refcounted like any other Python object. So do that.

py3: make py3 compat.iterbytestr simpler and faster With Python 3.4.3, timit says 11.9 usec-> 6.44 usec. With Python 3.6.0, timeit says 14.1 usec -> 9.55 usec.

py3: optimize py3 compat.bytechr using Struct.pack With Python 3.4.3, timeit says 0.437 usec -> 0.0685 usec. With Python 3.6, timeit says 0.157 usec -> 0.0907 usec. So it's faster on both versions, but the speedup varies a lot. Thanks to Gregory Szorc for the suggestion.

tests: properly drop back to root dir in test-status.t

dirstate: use list comprehension to get a list of keys We have used dict.keys() which returns a dict_keys() object instead of list on Python 3. So this patch replaces that with list comprehension which works both on Python 2 and 3.

match: slice over bytes to get the byteschr instead of ascii value

match: make regular expression bytes to prevent TypeError

scmutil: make function name bytes in class filecache func.__name__ returns unicodes and this leads to keyerror when we try to do filecache[''] by passing bytes.

localrepo: deprecate 'wfile' The method had very few users and the modern form is shorter. So let us deprecates another method of the localrepo class.

eol: use 'wvfs' instead of 'wfile' Method is about to be deprecated and the modern form is shorter.

localrepo: use 'wvfs' instead of 'wfile' Method is about to be deprecated and the modern form is shorter.

tagmerge: use 'wvfs' instead of 'wfile' Method is about to be deprecated and the modern form is shorter.

gpg: use 'wvfs' instead of 'wfile' Method is about to be deprecated and the modern form is shorter.

test: add a basic 'test-check-pylint.t' We add a minimal check using pylint for one case we knows we care about: "mutable default" argument. We'll likely extend this over time to cover other useful checks but this is a good starting point.

localrepo: don't use mutable default argument value Caught by pylint.