The tests are currently failing with USE="gd" as it tries to test gd functionality. It looks like we're using "make" to selectively compile the pieces that don't use gd, rather than a configure flag. But the configure file doesn't seem to support any of that. At the moment this could be worked around by setting a REQUIRED_USE to force gd be enabled for tests, but the correct approach may be to send a patch upstream to allow disabling of this functionality at configure time. Reproducible: Always
It looks like this has already been resolved in the upstream. The next release will have proper support for disabling this at configure. 1.16 will support --disable-image-output and will allow us to clean up the ebuild and resolve the issue. Upstream issue: https://github.com/vergoh/vnstat/pull/35