bug#19667:

[Carlos Pita]

Something along these lines could be dirty but gets the job done:

diff --git a/.emacs.d/lisp/python.el b/.emacs.d/lisp/python.el
index 238c9b5..6bd9f5d 100644
--- a/.emacs.d/lisp/python.el
+++ b/.emacs.d/lisp/python.el
@@ -4469,7 +4469,9 @@ This is for compatibility with Emacs < 24.4."
                (overlay-end comint-last-prompt-overlay)))
         ((bound-and-true-p comint-last-prompt)
          comint-last-prompt)
-        (t nil)))
+        (t (save-excursion
+             (beginning-of-line 1)
+             (cons (point) (point))))))

This fakes a last prompt that starts and ends at the beginning of the
current line when the current buffer doesn't bind comint-last-prompt.