Resolve “ImportError: No module named antlr3″

I had this problem last night after installing Google AppEngine on Leopard:

lc278:laranevans laran$ python manage.py runserver
Traceback (most recent call last):
  File "manage.py", line 18, in 
    InstallAppengineHelperForDjango()
  File "/Users/laran/Workspace/laranevans/appengine_django/__init__.py", line 440, in InstallAppengineHelperForDjango
    InstallAppengineDatabaseBackend()
  File "/Users/laran/Workspace/laranevans/appengine_django/__init__.py", line 175, in InstallAppengineDatabaseBackend
    PatchTestDBCreationFunctions()
  File "/Users/laran/Workspace/laranevans/appengine_django/__init__.py", line 188, in PatchTestDBCreationFunctions
    from django.test import utils
  File "/usr/local/google_appengine/lib/django/django/test/__init__.py", line 6, in 
    from django.test.testcases import TestCase
  File "/usr/local/google_appengine/lib/django/django/test/testcases.py", line 2, in 
    from django.db import transaction
  File "/usr/local/google_appengine/lib/django/django/db/__init__.py", line 30, in 
    connection = backend.DatabaseWrapper(**settings.DATABASE_OPTIONS)
  File "/Users/laran/Workspace/laranevans/appengine_django/db/base.py", line 123, in __init__
    self._setup_stubs()
  File "/Users/laran/Workspace/laranevans/appengine_django/db/base.py", line 134, in _setup_stubs
    from google.appengine.tools import dev_appserver_main
  File "/usr/local/google_appengine/google/appengine/tools/dev_appserver_main.py", line 465, in 
    SetGlobals()
  File "/usr/local/google_appengine/google/appengine/tools/dev_appserver_main.py", line 81, in SetGlobals
    from google.appengine.tools import appcfg
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/appcfg.py", line 48, in 
    from google.appengine.cron import groctimespecification
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/cron/groctimespecification.py", line 43, in 
    import groc
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/cron/groc.py", line 24, in 
    import antlr3
ImportError: No module named antlr3
lc278:laranevans laran$

I resolved this by downloading the appropriate antlr3 package and using easy_install to install that package. After doing that AppEngine started up with not trouble at all.