add etherpad-check to clean method

fet2020/tasks/models.py

@@ -123,7 +123,6 @@ class Document(models.Model):
             self.slug = slugify(self.title)
 
         pad_name = slugify(str(self.date) + "-" + self.task.slug + "-" + self.slug)
-
         if len(pad_name) > 50:
             raise ValidationError(
                 _(
@@ -132,12 +131,11 @@ class Document(models.Model):
                 params={"length": len(pad_name), "pad_name": pad_name},
             )
 
-    def save(self, *args, **kwargs):
-        self.etherpad_key = create_pad(
-            slugify(str(self.date) + "-" + self.task.slug + "-" + self.slug)
-        )
-
-        super().save(*args, **kwargs)
+        self.etherpad_key = create_pad(pad_name)
+        if not self.etherpad_key:
+            raise ValidationError(
+                _(f"Etherpad '{pad_name}' konnte nicht erstellt werden."),
+            )
 
     def __str__(self):
         return self.title