The google.appengine.api.taskqueue package provides the following exception classes:

exception Error

This is the base for all exceptions in this package.

exception BadTransactionStateError(Error)

The state of the current transaction does not permit this operation.

exception InternalError(Error)

There was an internal error while accessing this queue. If this problem continues, please contact the App Engine team through our support forum with a description of your problem.

exception BadTaskStateError(Error)

The task is in the wrong state for the requested operation.

exception DatastoreError(Error)

There was a datastore error while accessing the queue.

exception DuplicateTaskNameError(Error)

When adding multiple tasks to a queue in a batch, two tasks in the batch have the same name, which is not allowed.

exception InvalidLeaseTimeError(Error)

The lease time period is invalid.

exception InvalidMaxTasksError(Error)

The requested max tasks in lease_tasks is invalid.

exception InvalidQueueError(Error)

The queue's configuration is invalid.

exception InvalidQueueModeError(Error)

Invoking PULL queue operation on a PUSH queue or vice versa.

exception InvalidQueueNameError(InvalidQueueError)

The queue's name is invalid.

exception InvalidTaskError(Error)

The task's parameters, headers, or method is invalid.

exception InvalidTaskNameError(InvalidTaskError)

The task's name is invalid.

exception InvalidTaskRetryOptionsError(Error)

The task retry configuration is invalid.

exception InvalidUrlError(InvalidTaskError)

The task's relative URL is invalid.

exception PermissionDeniedError(Error)

The requested operation is not allowed for this app.

exception TaskAlreadyExistsError(InvalidTaskError)

Task already exists. It has not yet run.

exception TaskTooLargeError(InvalidTaskError)

The task is too large with its headers and payload.

exception TombstonedTaskError(InvalidTaskError)

A task with the same name was previously executed in the queue; names should be unique within a queue.

exception TooManyTasksError(Error)

When adding multiple tasks to a queue in a batch, the number of tasks in the batch exceeds the limit.

exception TransientError(Error)

There was a transient error while accessing the queue. Please try again later.

exception UnknownQueueError(Error)

The queue specified is unknown.