Log message:
Update py-itsdangerous to 0.24.

Version 0.24
~~~~~~~~~~~~

- Added a `BadHeader` exception that is used for bad headers
  that replaces the old `BadPayload` exception that was reused
  in those cases.

Log message:
Mark packages as not ready for python-3.x where applicable;
either because they themselves are not ready or because a
dependency isn't. This is annotated by
PYTHON_VERSIONS_INCOMPATIBLE=  33 # not yet ported as of x.y.z
or
PYTHON_VERSIONS_INCOMPATIBLE=  33 # py-foo, py-bar
respectively, please use the same style for other packages,
and check during updates.

Use versioned_dependencies.mk where applicable.
Use REPLACE_PYTHON instead of handcoded alternatives, where applicable.
Reorder Makefile sections into standard order, where applicable.

Remove PYTHON_VERSIONS_INCLUDE_3X lines since that will be default
with the next commit.

Whitespace cleanups and other nits corrected, where necessary.

Log message:
PYTHON_VERSIONS_INCOMPATIBLE cleanup.

Log message:
Update py-itsdangerous to 0.23.

Version 0.23
~~~~~~~~~~~~

- Fixed a packaging mistake that caused the tests and license
  files to not be included.

Log message:
Update py-itsdangerous to 0.22.

Version 0.22
~~~~~~~~~~~~

- Added support for `TimedJSONWebSignatureSerializer`.
- made it possible to override the signature verification function
  to allow implementing asymmetrical algorithms.

Log message:
Import itsdangerous-0.21 as security/py-itsdangerous.

It's Dangerous
   ... so better sign this

Various helpers to pass data to untrusted environments and to get it back
safe and sound.

This repository provides a module that is a port of the django signing
module.  It's not directly copied but some changes were applied to
make it work better on its own.