ensure foreign keys are enabled on sqlite

jupyterhub/orm.py

@@ -20,6 +20,7 @@ from sqlalchemy import (
 )
 from sqlalchemy.ext.declarative import declarative_base, declared_attr
 from sqlalchemy.orm import sessionmaker, relationship
+from sqlalchemy.interfaces import PoolListener
 from sqlalchemy.pool import StaticPool
 from sqlalchemy.sql.expression import bindparam
 from sqlalchemy import create_engine, Table
@@ -464,6 +465,13 @@ class DatabaseSchemaMismatch(Exception):
     the current version of JupyterHub.
     """
 
+
+class ForeignKeysListener(PoolListener):
+    """Enable foreign keys on sqlite"""
+    def connect(self, dbapi_con, con_record):
+        dbapi_con.execute('pragma foreign_keys=ON')
+
+
 def check_db_revision(engine):
     """Check the JupyterHub database revision
 
@@ -527,10 +535,14 @@ def check_db_revision(engine):
             head=head,
         ))
 
+
 def new_session_factory(url="sqlite:///:memory:", reset=False, **kwargs):
     """Create a new session at url"""
     if url.startswith('sqlite'):
         kwargs.setdefault('connect_args', {'check_same_thread': False})
+        listeners = kwargs.setdefault('listeners', [])
+        listeners.append(ForeignKeysListener())
+
     elif url.startswith('mysql'):
         kwargs.setdefault('pool_recycle', 60)