* lisp/progmodes/python.el
(python-rx-constituents): Add dedenter and block-ender.
(python-indent-dedenters, python-indent-block-enders): Delete.
(python-indent-context): Return new case for dedenter-statement.
(python-indent-calculate-indentation): Handle new case.
(python-indent-calculate-levels): Fix levels calculation for
dedenter statements.
(python-indent-post-self-insert-function): Fix colon handling.
(python-info-dedenter-opening-block-message): New function.
(python-indent-line): Use it.
(python-info-closing-block)
(python-info-closing-block-message): Remove.
(python-info-dedenter-opening-block-position)
(python-info-dedenter-opening-block-positions)
(python-info-dedenter-statement-p): New functions.