Add missing license header

src/session.ts

@@ -1,3 +1,6 @@
+// Copyright (c) Jupyter Development Team.
+// Distributed under the terms of the Modified BSD License.
+
 import { IClientSession } from '@jupyterlab/apputils';
 
 import { CodeEditor } from '@jupyterlab/codeeditor';

tests/run-test.py

@@ -1,3 +1,6 @@
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
 import os
 from jupyterlab.tests.test_app import run_jest, JestApp
 

tests/src/session.spec.ts

@@ -1,3 +1,6 @@
+// Copyright (c) Jupyter Development Team.
+// Distributed under the terms of the Modified BSD License.
+
 import { expect } from 'chai';
 
 import { ClientSession, IClientSession } from '@jupyterlab/apputils';