Fix unclosed file warning (#9371)

Author: mergify[bot]

Tests/test_imagemorph.py

@@ -231,15 +231,15 @@ def test_negate() -> None:
 
 
 def test_incorrect_mode() -> None:
-    im = hopper()
     mop = ImageMorph.MorphOp(op_name="erosion8")
 
-    with pytest.raises(ValueError, match="Image mode must be 1 or L"):
-        mop.apply(im)
-    with pytest.raises(ValueError, match="Image mode must be 1 or L"):
-        mop.match(im)
-    with pytest.raises(ValueError, match="Image mode must be 1 or L"):
-        mop.get_on_pixels(im)
+    with hopper() as im:
+        with pytest.raises(ValueError, match="Image mode must be 1 or L"):
+            mop.apply(im)
+        with pytest.raises(ValueError, match="Image mode must be 1 or L"):
+            mop.match(im)
+        with pytest.raises(ValueError, match="Image mode must be 1 or L"):
+            mop.get_on_pixels(im)
 
 
 def test_add_patterns() -> None: