feat: prevent deleting definition with running exercises

No API changes

Closes #209

exercise_definition/lib/definition_manager.py

@@ -2,6 +2,7 @@ import os
 
 from django.conf import settings
 
+from common_lib.exceptions import ExerciseOperationException
 from common_lib.logger import logger
 from common_lib.utils import get_model
 from exercise.lib.exercise_manager import ExerciseManager
@@ -12,7 +13,17 @@ class DefinitionManager:
     @staticmethod
     def delete_definition(definition_id: int):
         definition = get_model(Definition, id=definition_id)
-        for exercise in definition.exercises.all():
+        exercises = definition.exercises.all()
+        running_exercise_ids = [
+            exercise.id for exercise in exercises if exercise.running
+        ]
+        if len(running_exercise_ids) != 0:
+            raise ExerciseOperationException(
+                f"Cannot delete this definition because "
+                f"these running exercises depend on it {running_exercise_ids}"
+            )
+
+        for exercise in exercises:
             ExerciseManager.delete_exercise(exercise.id)
 
         for file_info in definition.files.all():