Fix with None input. (#10052)

tests/python-gpu/test_from_cupy.py

@@ -202,7 +202,10 @@ class TestFromCupy:
         n = 100
         X = cp.random.random((n, 2))
         m = xgb.QuantileDMatrix(X.toDlpack())
-        with pytest.raises(xgb.core.XGBoostError):
+
+        with pytest.raises(
+            xgb.core.XGBoostError, match="Slicing DMatrix is not supported"
+        ):
             m.slice(rindex=[0, 1, 2])
 
     @pytest.mark.skipif(**tm.no_cupy())

tests/python/test_with_sklearn.py

@@ -1456,3 +1456,16 @@ def test_intercept() -> None:
     result = reg.intercept_
     assert result.dtype == np.float32
     assert result[0] < 0.5
+
+
+def test_fit_none() -> None:
+    with pytest.raises(TypeError, match="NoneType"):
+        xgb.XGBClassifier().fit(None, [0, 1])
+
+    X = rng.normal(size=4).reshape(2, 2)
+
+    with pytest.raises(ValueError, match="Invalid classes"):
+        xgb.XGBClassifier().fit(X, None)
+
+    with pytest.raises(ValueError, match="labels"):
+        xgb.XGBRegressor().fit(X, None)