Adding comment about this fix.

IPython/html/tests/launchnotebook.py

@@ -1,100 +1,102 b''
 """Base class for notebook tests."""
 
 from __future__ import print_function
 
 import sys
 import time
 import requests
 from contextlib import contextmanager
 from subprocess import Popen, STDOUT
 from unittest import TestCase
 
 import nose
 
 from IPython.utils.tempdir import TemporaryDirectory
 
 MAX_WAITTIME = 30   # seconds to wait for notebook server to start
 POLL_INTERVAL = 0.1 # time between attempts
 
+# TimeoutError is a builtin on Python 3. This can be removed when we stop
+# supporting Python 2.
 class TimeoutError(Exception):
     pass
 
 class NotebookTestBase(TestCase):
     """A base class for tests that need a running notebook.
     
     This creates an empty profile in a temp ipython_dir
     and then starts the notebook server with a separate temp notebook_dir.
     """
 
     port = 12341
 
     @classmethod
     def wait_until_alive(cls):
         """Wait for the server to be alive"""
         url = 'http://localhost:%i/api/notebooks' % cls.port
         for _ in range(int(MAX_WAITTIME/POLL_INTERVAL)):
             try:
                 requests.get(url)
             except requests.exceptions.ConnectionError:
                 if cls.notebook.poll() is not None:
                     raise RuntimeError("The notebook server exited with status %s" \
                                         % cls.notebook.poll())
                 time.sleep(POLL_INTERVAL)
             else:
                 return
 
         raise TimeoutError("The notebook server didn't start up correctly.")
     
     @classmethod
     def wait_until_dead(cls):
         """Wait for the server process to terminate after shutdown"""
         for _ in range(int(MAX_WAITTIME/POLL_INTERVAL)):
             if cls.notebook.poll() is not None:
                 return
             time.sleep(POLL_INTERVAL)
     
         raise TimeoutError("Undead notebook server")
 
     @classmethod
     def setup_class(cls):
         cls.ipython_dir = TemporaryDirectory()
         cls.notebook_dir = TemporaryDirectory()
         notebook_args = [
             sys.executable, '-c',
             'from IPython.html.notebookapp import launch_new_instance; launch_new_instance()',
             '--port=%d' % cls.port,
             '--port-retries=0',  # Don't try any other ports
             '--no-browser',
             '--ipython-dir=%s' % cls.ipython_dir.name,
             '--notebook-dir=%s' % cls.notebook_dir.name,
         ]
         cls.notebook = Popen(notebook_args,
             stdout=nose.iptest_stdstreams_fileno(),
             stderr=STDOUT,
         )
         cls.wait_until_alive()
 
     @classmethod
     def teardown_class(cls):
         cls.notebook.terminate()
         cls.ipython_dir.cleanup()
         cls.notebook_dir.cleanup()
         cls.wait_until_dead()
 
     @classmethod
     def base_url(cls):
         return 'http://localhost:%i/' % cls.port
 
 
 @contextmanager
 def assert_http_error(status, msg=None):
     try:
         yield
     except requests.HTTPError as e:
         real_status = e.response.status_code
         assert real_status == status, \
                     "Expected status %d, got %d" % (real_status, status)
         if msg:
             assert msg in str(e), e
     else:
         assert False, "Expected HTTP error status"
  No newline at end of file