Merge "Only fail on known-bad grep configurations."

# only has an effect on python 2.6 and above.

export PYTHONDONTWRITEBYTECODE := 1

ifneq ($(GREP_OPTIONS),)

ifneq ($(filter --color=always, $(GREP_OPTIONS)),)

$(warning The build system needs unmodified output of grep.)

$(error Please unset your $$GREP_OPTIONS.)

$(error Please remove --color=always from your  $$GREP_OPTIONS)

endif

# Standard source directories.