(no-ticket) Fix package reupload in PA contests by contest admins

When uploading a package to a PA contest, the PA contest controller
adds a selection box for setting the tasks's division to the upload form,
and adds a save_division handler to post-upload handlers,
which saves the task division in problemistance.

When uploading a new problem, this works fine.
When a superadmin reuploads a package, the PA contest controller doesn't
get involved, so all of that is skipped.

However, when a contest admin who isn't a superadmin reuploads a package,
the PA conteset controller does the above two things,
but the save_division handler fails, because it uses 'problem_instance_id'
key from the env, which is set by update_problem_instance handler
only when creating a new problem instance, which doesn't happen on reupload.

Fix this by making update_problem_instance handler also add the
'problem_instance_id' key when it finds a pre-existing problem instance.

Change-Id: I99d89c77a75d645f390601c1bc5c2c0f7794b0f5

oioioi/problems/handlers.py

@@ -25,15 +25,16 @@ def update_problem_instance(env):
     """
     problem = Problem.objects.get(id=env['problem_id'])
     if env.get('contest_id', None):
-        if not ProblemInstance.objects.filter(
+        pi = ProblemInstance.objects.filter(
             contest__id=env['contest_id'], problem=problem
-        ).exists():
+        ).first()
+        if not pi:
             contest = Contest.objects.get(id=env['contest_id'])
             pi = get_new_problem_instance(problem, contest)
             if env.get('round_id', None) and not pi.round:
                 pi.round = Round.objects.get(id=env['round_id'])
             pi.save()
-            env['problem_instance_id'] = pi.id
+        env['problem_instance_id'] = pi.id
     if env['is_reupload']:
         update_all_probleminstances_after_reupload(problem)