CLI export shall NOT be colorfull

[DoubleHP <dhp_diaaa doublehp org>]

I designed some schematics last year under Debian for a report. A Makefile ddi the
export from .dia to .png using -e option, so that the file can be included in the
latex report (pdflatex). This used to be fine until I move to Gentoo.

Since 2 months, the CLI -e option produces colorfull .png, whan manual export using
GUI produces good B&W. The text is still black, but all the rest is random color:
pink, purple, green, blue, brown, ... and black ... imagine a report with black text
on top of black or brown boxes.

Why does the Gentoo version produce color ?

I have double check the .dia file: all boxes have black text and white background.

but CLI always produce colored boxes.


$ dia --nosplash -e dia/monitor_diagram.png dia/monitor_diagram.dia

** (dia-python:2642): WARNING **: Can't color_convert in non-interactive app (w/o
color_init())

** (dia-python:2642): WARNING **: Can't color_convert in non-interactive app (w/o
color_init())

** (dia-python:2642): WARNING **: Can't color_convert in non-interactive app (w/o
color_init())

** (dia-python:2642): WARNING **: Can't color_convert in non-interactive app (w/o
color_init())
[...]
** (dia-python:2642): WARNING **: Can't color_convert in non-interactive app (w/o
color_init())

** (dia-python:2642): WARNING **: Can't color_convert in non-interactive app (w/o
color_init())

** (dia-python:2642): WARNING **: Can't color_convert in non-interactive app (w/o
color_init())
dia/monitor_diagram.dia --> dia/monitor_diagram.png

I always had those messages with Debian, but used to produce B&W pictures.