Put the remove in test test_save_registry in try-finally block (#83)

In case the tests fail after the creation of the file but before the
remove, the file still is not removed and will make the test fail in the
next run.

tests/test_code.py

@@ -348,26 +348,31 @@ def test_save_registry(self, function):
         """
         Verifies that the CodeExercise works with an answer_registry.
         """
+        name = "test_save_registry-student_name"
+        try:
+
+            def print_success(code_ex: CodeExercise | None):
+                code_ex.output.object = "Success"
+
+            cue_output = CueObject("Not initialized")
+            exercise_registry = ExerciseRegistry()
+
+            code_ex = CodeExercise(
+                code=function,
+                parameters={"parameter": fixed(5)},
+                exercise_registry=exercise_registry,
+                key="test_save_registry_ex",
+                outputs=[cue_output],
+                update=print_success,
+            )
 
-        def print_success(code_ex: CodeExercise | None):
-            code_ex.output.object = "Success"
-
-        cue_output = CueObject("Not initialized")
-        exercise_registry = ExerciseRegistry()
-
-        code_ex = CodeExercise(
-            code=function,
-            parameters={"parameter": fixed(5)},
-            exercise_registry=exercise_registry,
-            key="test_save_registry_ex",
-            outputs=[cue_output],
-            update=print_success,
-        )
-
-        exercise_registry._student_name_text.value = "test_save_registry-student_name"
-        exercise_registry.create_new_file_from_dropdown()
-        code_ex._save_button.click()
-        os.remove("test_save_registry-student_name.json")
+            exercise_registry._student_name_text.value = name
+            exercise_registry.create_new_file_from_dropdown()
+            code_ex._save_button.click()
+        finally:
+            file_name = f"{name}.json"
+            if os.path.exists(file_name):
+                os.remove(file_name)
 
     @pytest.mark.parametrize(
         "code_ex",