veusz: skip vectorfield rendering test (#516755)

pkgs/by-name/ve/veusz/package.nix

@@ -33,6 +33,9 @@ python3Packages.buildPythonApplication (finalAttrs: {
     wrapQtApp "$out/bin/veusz"
   '';
 
+  # vectorfield.vsz renders a PPM bitmap whose pixel values differ across Qt versions/platforms
+  patches = [ ./skip-vectorfield-test.patch ];
+
   # pyqt_setuptools.py uses the platlib path from sysconfig, but NixOS doesn't
   # really have a corresponding path, so patching the location of PyQt5 inplace
   postPatch = ''

pkgs/by-name/ve/veusz/skip-vectorfield-test.patch

@@ -0,0 +1,10 @@
+--- a/tests/runselftest.py
++++ b/tests/runselftest.py
+@@ -113,6 +113,7 @@
+         '3d_points.vsz',
+         '3d_surface.vsz',
+         '3d_volume.vsz',
++        'vectorfield.vsz',
+     ])
+
+ class StupidFontMetrics: