Feat: Add working version of lesson thumbnail

courses/models.py

@@ -744,15 +744,7 @@ class Lesson(PositionedModel):
     def is_course_last_lesson(self):
         lessons = list(self.course.public_lessons)
         return len(lessons) > 0 and self == lessons[-1]
-        
-    @property
-    def thumbnail_url(self):
-        return self.get_thumbnail_url()
 
-    def get_thumbnail_url(self):
-        if self.thumbnail:
-            return self.thumbnail
-        return ''
 
     class Meta:
         verbose_name = _('Lesson')
@@ -763,12 +755,14 @@ class Lesson(PositionedModel):
         return self.name
 
     @property
-    def thumbnail(self):
+    def thumbnail_url(self):
         try:
             first_vid_unit = self.units.exclude(video=None).order_by('position')[0]
             thumbnail = 'http://i1.ytimg.com/vi/' + first_vid_unit.video.youtube_id + '/hqdefault.jpg'
             return thumbnail
         except IndexError:
+            if self.thumbnail:
+                return self.thumbnail.url
             return staticfiles_storage.url('img/lesson-default.png')
 
     def activity_count(self):