(no-ticket) Quote contest's id in admin url

Django admin uses some kind of escaping special characters with
underscores.
This caused 404 with primary key containing something like '_21'.

Change-Id: I76f8b2e0358f7504c851648b18bfd04a78cd9dca

oioioi/contests/admin.py

@@ -2,7 +2,7 @@
 import urllib
 
 from django.contrib.admin import AllValuesFieldListFilter, SimpleListFilter
-from django.contrib.admin.util import unquote
+from django.contrib.admin.util import unquote, quote
 from django.core.urlresolvers import reverse
 from django.forms.models import modelform_factory
 from django.http import HttpResponseRedirect
@@ -135,7 +135,7 @@ def _mixins_for_instance(self, request, instance):
 
 contest_admin_menu_registry.register('contest_change', _("Settings"),
         lambda request: reverse('oioioiadmin:contests_contest_change',
-            args=(request.contest.id,)), order=20)
+            args=(quote(request.contest.id),)), order=20)
 
 
 class ProblemInstanceAdmin(admin.ModelAdmin):

oioioi/contests/tests.py

@@ -11,6 +11,7 @@
 from django.core.files.base import ContentFile
 from django.utils.timezone import utc, LocalTimezone
 from django.contrib.auth.models import User, AnonymousUser
+from django.contrib.admin.util import quote
 
 from oioioi.base.tests import check_not_accessible, fake_time
 from oioioi.contests.models import Contest, Round, ProblemInstance, \
@@ -491,8 +492,8 @@ def test_simple_contest_create_and_change(self):
         self.assertEqual(round.results_date,
                 datetime(2012, 2, 5, 6, 7, 8, tzinfo=LocalTimezone()))
 
-        url = reverse('oioioiadmin:contests_contest_change', args=('cid',)) \
-                + '?simple=true'
+        url = reverse('oioioiadmin:contests_contest_change',
+                args=(quote('cid'),)) + '?simple=true'
         response = self.client.get(url)
         self.assertIn('2012-02-05', response.content)
         self.assertIn('06:07:08', response.content)
@@ -521,8 +522,8 @@ def test_simple_contest_create_and_change(self):
         self.assertEqual(round.results_date,
                 datetime(2013, 2, 5, 16, 7, 8, tzinfo=LocalTimezone()))
 
-        url = reverse('oioioiadmin:contests_contest_change', args=('cid',)) \
-                + '?simple=true'
+        url = reverse('oioioiadmin:contests_contest_change',
+                args=(quote('cid'),)) + '?simple=true'
         response = self.client.get(url)
         post_data = {
                 'name': 'cname1',