TST: cleanup unused return values in tests (following pytest deprecat…

…ion)

yt/visualization/volume_rendering/tests/test_composite.py

@@ -81,4 +81,3 @@ def test_composite_vr(self):
         im = sc.render()
         im = ImageArray(im.d)
         im.write_png("composite.png")
-        return im

yt/visualization/volume_rendering/tests/test_points.py

@@ -66,4 +66,3 @@ def test_points_vr(self):
         sc.add_source(points_source)
         im = sc.render()
         im.write_png("points.png")
-        return im

yt/visualization/volume_rendering/tests/test_save_render.py

@@ -43,5 +43,3 @@ def test_save_render(self):
         # save a different format with/without sigma clips
         sc.save(os.path.join(self.tmpdir, "no_clip.jpg"), render=False)
         sc.save(os.path.join(self.tmpdir, "clip_2.jpg"), sigma_clip=2, render=False)
-
-        return sc

yt/visualization/volume_rendering/tests/test_simple_vr.py

@@ -34,5 +34,4 @@ def tearDown(self):
 
     def test_simple_vr(self):
         ds = fake_random_ds(32)
-        im, sc = yt.volume_render(ds, fname="test.png", sigma_clip=4.0)
-        return im, sc
+        _im, _sc = yt.volume_render(ds, fname="test.png", sigma_clip=4.0)