Delete solutions and widget when deleting problem

zesje/api/problems.py

@@ -105,6 +105,10 @@ class Problems(Resource):
         if any([sol.graded_by is not None for sol in problem.solutions]):
             return dict(status=403, message=f'Problem has already been graded'), 403
         else:
+            # Delete all solutions associated with this problem
+            for sol in problem.solutions:
+                db.session.delete(sol)
+            db.session.delete(problem.widget)
             db.session.delete(problem)
             db.session.commit()
             return dict(status=200, message="ok"), 200