[BUG] : Please don't color 'WARNING'

[patquem]

Hello,
When coloring warning messages with yellow (in modopt/interface/errors.py line 39), this engenders special characters �[33mWARNING�[0m that make big trouble during xml reports generation/interpretation.
Could you please remove the colorization ?
(it could be the same for ERROR message).
Thanks,
Patrick