Turn on Python warnings
Pass a suitable
-W flag to Python in the build system so we get notified for deprecations in the future.
This change only affects what is run during the build; it does not change
TARGET_PYTHON, so these warnings stay silent for users.
We need to disable ResourceWarning for the time being, as the scripts frequently embed
open(some_file).read() in larger expressions.
A fix for the last invalid escape sequences in string literals that were uncovered by this change is included.