def _init_flow_exceptions():
  """Internal helper to initialize _flow_exceptions.

  This automatically adds webob.exc.HTTPException, if it can be imported.
  """
  global _flow_exceptions
  _flow_exceptions = ()
  add_flow_exception(datastore_errors.Rollback)
  try:
    from webob import exc
  except __HOLE__:
    pass
  else:
    add_flow_exception(exc.HTTPException)
dataset/ETHPy150Open GoogleCloudPlatform/datastore-ndb-python/ndb/tasklets.py/_init_flow_exceptions