Fixes: debbugs:19761
* lisp/progmodes/python.el
(python-hideshow-forward-sexp-function): New function based on
Carlos Pita <carlosjosepita@gmail.com> patch.
(python-mode): Make `hs-special-modes-alist` use it and initialize
the end regexp with the empty string to avoid skipping parens.
* test/automated/python-tests.el
(python-tests-visible-string): New function.
(python-parens-electric-indent-1)
(python-triple-quote-pairing): Fix indentation, move require calls.
(python-hideshow-hide-levels-1)
(python-hideshow-hide-levels-2): New tests.