PyXDG searches for 'highcolor' icons and then falls back to 'hicolor' theme. It could just search for 'hicolor' icons from the start and not bothering with 'highcolor' as it is not standard icon theme anyway.
Fixed: http://cgit.freedesktop.org/xdg/pyxdg/commit/?id=890841fb910112853306e2d6b4163cce12262fd5
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