Bug#707489: widelands: FTBFS: make[1]: convert: Command not found

[Vincent Cheng]

> convert debian/widelands/usr/share/icons/hicolor/32x32/apps/widelands.png \
>               debian/widelands/usr/share/icons/hicolor/32x32/apps/widelands.xpm
> make[1]: convert: Command not found
> make[1]: *** [override_dh_auto_install] Error 127

It looks like widelands is missing a build dependency on imagemagick.

Regards,
Vincent