Drop Ponos non Postgres DB support

arkindex/ponos/managers.py

-from django.db import connections
 from django.db.models import Manager
 
 
@@ -6,31 +5,20 @@ class TaskManager(Manager):
     def parents(self, task):
         """
         List all tasks that a task depends on, directly or not.
-
-        When using a PostgreSQL database, this will use a recursive query.
-        This falls back to a recursive generator on other databases.
+        A PostgreSQL recursive query is used for better performances.
         """
-        if connections[self.db].vendor == "postgresql":
-            return self.raw(
-                """
-                with recursive parents(id) as (
-                    select to_task_id
-                        from ponos_task_parents j
-                        where j.from_task_id = %s
-                    union all
-                        select j.to_task_id
-                        from ponos_task_parents as j, parents
-                        where j.from_task_id = parents.id
-                )
-                select distinct * from parents
-                """,
-                [task.id],
+        return self.raw(
+            """
+            with recursive parents(id) as (
+                select to_task_id
+                    from ponos_task_parents j
+                    where j.from_task_id = %s
+                union all
+                    select j.to_task_id
+                    from ponos_task_parents as j, parents
+                    where j.from_task_id = parents.id
             )
-        else:
-
-            def _parents_python(task):
-                yield from task.parents.all()
-                for parent in task.parents.all():
-                    yield from _parents_python(parent)
-
-            return _parents_python(task)
+            select distinct * from parents
+            """,
+            [task.id],
+        )