remove unused imports, explicitly create a db in-memory

Author: andrii-i

jupyter_scheduler/tests/test_execution_manager.py

@@ -1,9 +1,6 @@
-import os
-from contextlib import contextmanager
 from pathlib import Path
 from unittest.mock import PropertyMock, patch
 
-import pytest
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
 
@@ -17,7 +14,7 @@
 
 
 def test_execution_manager_with_side_effects():
-    db_url = "sqlite://"
+    db_url = "sqlite:///:memory:"
     engine = create_engine(db_url, echo=False)
     Base.metadata.create_all(engine)
     db_session = sessionmaker(bind=engine)