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* The supported Python versions are now 3.8 to 3.13.
* Saving and loading of cookies has been made more robust, and it now also
incorporates the domains and paths of the cookies.
* Twill now uses Flask_ instead of Quixote_ as test server for running its own
test suite.
* Twill now uses 'argparse' instead of the deprecated 'optparse' to parse
options and arguments passed on the command line.