title: Getting a "Can't pickle local object 'LiveServerTestCase'" error when trying to use LiveServerTestCase to test Flask app
body: <p>I am getting the error mentioned in the title once trying to run a unittest on my Flask app using LiveServerTestCase from flask_testing.</p>
  <p>This is my test file:</p>
  <pre><code>from app import create_app
  from flask_testing import LiveServerTestCase
  
  class TestBase(LiveServerTestCase):
  
      def create_app(self):
          app = create_app()
          app.config.update(LIVESERVER_PORT=8847, TESTING=True)
          return app
      
      def test_app(self):
          self.assertEqual('test', 'test')
  </code></pre>
  <p>And this is the error I am getting once running my test using nose2:</p>
  <pre><code>AttributeError: Can't pickle local object 'LiveServerTestCase._spawn_live_server.&lt;locals&gt;.worker'
  
  During handling of the above exception, another exception occurred:
  
  AttributeError: 'NoneType' object has no attribute 'terminate'
  Internal Error: runTests aborted: 'NoneType' object has no attribute 'terminate'
  </code></pre>
  <p>I really couldn't find anything helpful online about this issue,</p>