LIL-430. Add validator to Course deferred_start_at field

apps/course/migrations/0036_auto_20180426_1256.py

@@ -0,0 +1,19 @@
+# Generated by Django 2.0.4 on 2018-04-26 09:56
+
+import apps.course.models
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('course', '0035_comment_deactivated_at'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='course',
+            name='deferred_start_at',
+            field=models.DateTimeField(blank=True, help_text='Заполнить если курс отложенный', null=True, validators=[apps.course.models.deferred_start_at_validator], verbose_name='Отложенный запуск курса'),
+        ),
+    ]

apps/course/models.py

@@ -3,6 +3,7 @@ from uuid import uuid4
 from django.db import models
 from django.utils import timezone
 from django.utils.text import slugify
+from django.utils.timezone import now
 from django.contrib.auth import get_user_model
 from django.urls import reverse_lazy
 from polymorphic_tree.models import PolymorphicMPTTModel, PolymorphicTreeForeignKey
@@ -27,6 +28,13 @@ def default_slug():
     return str(uuid4())
 
 
+def deferred_start_at_validator(value):
+    if value < now():
+        raise ValidationError(
+            'Дата и время начала курса не может быть меньше текущих.',
+        )
+
+
 class Course(BaseModel, DeactivatedMixin):
     DRAFT = 0
     PENDING = 1
@@ -66,7 +74,7 @@ class Course(BaseModel, DeactivatedMixin):
     is_infinite = models.BooleanField(default=False)
     deferred_start_at = models.DateTimeField(
         'Отложенный запуск курса', help_text='Заполнить если курс отложенный',
-        null=True, blank=True
+        null=True, blank=True, validators=[deferred_start_at_validator],
     )
     category = models.ForeignKey('Category', null=True, blank=True, on_delete=models.PROTECT)
     duration = models.IntegerField('Продолжительность курса', default=0)