stablerange: fallback to a more naive approach to find subrange
As suspected, using "bheads" was bit good enough in some case and we have to
fall back to the approach used in "basic".
On the evolve repo (about 3K changeset) this approach is about 60% slower than
the previous (wrong) code.
[flake8]
ignore =
#closing bracket does not match indentation of opening bracket's line
E123,
# closing bracket does not match visual indentation
E124,
# visually indented line with same indent as next logical line
E129,
# at least two spaces before inline comment
E261,
# too many leading '#' for block comment
E266,
# expected 2 blank lines, found 0
E302,
# expected 2 blank lines after end of function or class
E305,
# module level import not at top of file
E402,
# line too long (82 > 79 characters)
E501,
# do not assign a lambda expression, use a def
E731,
# class names should use CapWords convention
N801,
# line break occurred before a binary operator
W503
builtins=xrange, execfile