Check if/why cascaded MapServer requests are processed by MapProxy

[olt]

There is a report that MapProxy does processes cascaded GeoTIFF requests from MapServer sources and thus removing the georeference information.

http://lists.osgeo.org/pipermail/mapproxy/2012-August/001173.html

[fvanderbiest]

bbinet and I have been investigating this issue.
We have elaborated a patch (see branch issue15) but it still breaks tests.

[olt]

The issue is that you are requesting with transparent=False (default value of transparent) but your source is transparent. MapProxy will modify the image to apply the bgcolor.
MapProxy should pass the GeoTIFF unmodified when you request with transparent=true.