old_contents: import sys
  try:
      # noinspection PyPackageRequirements
      import unittest2 as unittest
      sys.modules['unittest'] = unittest
  except ImportError:
      import unittest
  
  from goless.backends import current as be
  
  
  class BaseTests(unittest.TestCase):
      """
      Base class for unit tests.
      Yields in setup and teardown so no lingering tasklets
      are run in a later test,
      potentially causing an error that would leave people scratching their heads.
      """
  
      def setUp(self):
          be.yield_()
  
      def tearDown(self):
          be.yield_()
          self.assertTrue(be.would_deadlock())
  
new_contents: import sys
  try:
      # noinspection PyPackageRequirements
      import unittest2 as unittest
      sys.modules['unittest'] = unittest
  except ImportError:
      import unittest
  
  from goless.backends import current as be
  
  
  class BaseTests(unittest.TestCase):
      """
      Base class for unit tests.
      Yields in setup and teardown so no lingering tasklets
      are run in a later test,
      potentially causing an error that would leave people scratching their heads.
      """
  
      def setUp(self):
          be.yield_()
  
      def tearDown(self):
          be.yield_()
          self.assertTrue(be.would_deadlock(), 'Task(s) still running after test finished')
  
subject: Add comment in BaseTests tearDown