Mixed spacing in python functions can cause subtle issues and
generally confuses users. We've standardised on 4 space indentation,
adding this warning helps ensure consistency and avoid bugs. It
also makes _prepend and _append operations on python functions slightly
less risky.
(Bitbake rev: c51cfaf48d3b12a19b01e824b6ba4230376bcad4)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>