Squashed commit of the following:

commit ff25e2dc285c423f4c40a83deb89a56ee62b15a9
Author: Alban Gruin <alban dot gruin at gmail dot com>
Date:   Sat Feb 11 13:47:38 2017 +0100

    Nettoyage du code de CourseManager

commit 26a132d5d1fdb7fc9da827bbc9d5e409834fb954
Author: Alban Gruin <alban dot gruin at gmail dot com>
Date:   Sat Feb 11 13:45:14 2017 +0100

    Suppression du GroupedManager et de toutes ses sous-classes

1 files changed, 13 insertions, 16 deletions

diff --git a/models.py b/models.py
index 1723536..1e96a88 100644
--- a/models.py
+++ b/models.py
@@ -15,17 +15,19 @@
 #    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 from django.db import connection, models
-from django.db.models import Q
+from django.db.models import Count, Manager, Q
 from django.db.models.expressions import RawSQL
-from django.db.models.functions import ExtractYear
+from django.db.models.functions import Extract, ExtractYear
 from django.utils.text import slugify
 
-from .db import ExtractWeek, GroupedManager
-
 import hashlib
 import os
 
 
+class ExtractWeek(Extract):
+    lookup_name = "week"
+
+
 class Timetable(models.Model):
     name = models.CharField(max_length=64, unique=True, verbose_name="nom")
     url = models.URLField(max_length=255, unique=True, verbose_name="URL")
@@ -141,22 +143,17 @@ class Room(models.Model):
         verbose_name_plural = "salles"
 
 
-class CourseManager(GroupedManager):
-    def __get_weeks(self, qs):
-        extractYear = ExtractYear("begin")
-        qs = qs.group_by("groups", "year", "week", "groups__timetable", "groups__mention", "groups__subgroup", "groups__td", "groups__tp", "begin", "groups__name").order_by("groups__name", "year", "week")
-
-        if connection.vendor == "postgresql":
-            return qs.annotate(week=ExtractWeek("begin"), year=extractYear)
-        else:
-            return qs.annotate(week=RawSQL("""cast(strftime("%%W", "begin") as integer)""", []), year=extractYear)
-
+class CourseManager(Manager):
     def get_courses_for_group(self, group, **filters):
         return self.get_queryset().filter(Q(groups__td__isnull=True) | Q(groups__td=group.td), Q(groups__tp__isnull=True) | Q(groups__tp=group.tp), groups__mention=group.mention, groups__subgroup=group.subgroup, timetable=group.timetable, **filters).order_by("begin")
 
     def get_weeks(self, **criteria):
-        qs = self.get_queryset().filter(**criteria)
-        return self.__get_weeks(qs)
+        qs = self.get_queryset().filter(**criteria).order_by("groups__name", "year", "week").annotate(_=Count(("groups", "year", "week", "begin")), year=ExtractYear("begin"))
+
+        if connection.vendor == "postgresql":
+            return qs.annotate(week=ExtractWeek("begin"))
+        else:
+            return qs.annotate(week=RawSQL("""cast(strftime("%%W", "begin") as integer)""", []))
 
 
 class Course(models.Model):