Improved error messages

ianthomas23 · ianthomas23 · commit 55a0edbbeecd · 2019-05-28T14:35:25.000+01:00
diff --git a/lib/matplotlib/tests/test_triangulation.py b/lib/matplotlib/tests/test_triangulation.py
@@ -1124,17 +1124,18 @@ def test_tricontour_non_finite_z():
     triang = mtri.Triangulation(x, y)
     plt.figure()
 
-    with pytest.raises(ValueError, match='z array cannot contain non-finite ' +
-                                         'values'):
+    with pytest.raises(ValueError, match='z array must not contain non-finite '
+                                         'values within the triangulation'):
         plt.tricontourf(triang, [0, 1, 2, np.inf])
 
-    with pytest.raises(ValueError, match='z array cannot contain non-finite ' +
-                                         'values'):
+    with pytest.raises(ValueError, match='z array must not contain non-finite '
+                                         'values within the triangulation'):
         plt.tricontourf(triang, [0, 1, 2, -np.inf])
 
-    with pytest.raises(ValueError, match='z array cannot contain non-finite ' +
-                                         'values'):
+    with pytest.raises(ValueError, match='z array must not contain non-finite '
+                                         'values within the triangulation'):
         plt.tricontourf(triang, [0, 1, 2, np.nan])
 
-    with pytest.raises(ValueError, match='z cannot be a masked array'):
+    with pytest.raises(ValueError, match='z must not contain masked points '
+                                         'within the triangulation'):
         plt.tricontourf(triang, np.ma.array([0, 1, 2, 3], mask=[1, 0, 0, 0]))
diff --git a/lib/matplotlib/tri/tricontour.py b/lib/matplotlib/tri/tricontour.py
@@ -88,9 +88,11 @@ def _contour_args(self, args, kwargs):
         # in the triangulation.
         z_check = z[np.unique(tri.get_masked_triangles())]
         if np.ma.is_masked(z_check):
-            raise ValueError('z cannot be a masked array')
+            raise ValueError('z must not contain masked points within the '
+                             'triangulation')
         if not np.isfinite(z_check).all():
-            raise ValueError('z array cannot contain non-finite values')
+            raise ValueError('z array must not contain non-finite values within'
+                             ' the triangulation')
 
         z = np.ma.masked_invalid(z, copy=False)
         self.zmax = float(z_check.max())
