bug#24856: 25.1.50; Emacs stucks when using C-k to kill lines in python-mode if the next line is a beginning of a docstring

[raynewang <raynewang@tencent.com>]

Please look at the following python snippet:

class Test(object):
  def func(self):
    """
    This is a test.
    """

I was trying to kill lines (C-k) from line 1. Emacs stucked everytime
after I killed line 2 and was going to kill line 3 (just before the
docstring delimiters). Most time C-g would not work or just brought
Emacs back for no more than 1 sec only. When it occurred, the only thing
I could do was to kill Emacs process.

I tried to disable all of my Emacs configurations, nothing changed.

May it be a problem of built-in python-mode?

Wish you guys could help me. I love your works!

Sincerely

Lei

======================================================================


In GNU Emacs 25.1.50.1 (x86_64-apple-darwin15.6.0, NS appkit-1404.47 Version 10.11.6 (Build 15G31))
of 2016-09-20 built on raynewang-rmbp.local
Repository revision: 83fbb3a6dd75e01a768cb6b3348b7c947711ee46
Windowing system distributor 'Apple', version 10.3.1504
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
<s-backspace> is undefined [2 times]
funcall-interactively: Wrong type argument: char-or-string-p, nil

Configured using:
'configure --disable-dependency-tracking --disable-silent-rules
--enable-locallisppath=/usr/local/share/emacs/site-lisp
--infodir=/usr/local/Cellar/emacs/HEAD-83fbb3a/share/info/emacs
--prefix=/usr/local/Cellar/emacs/HEAD-83fbb3a --without-x --with-xml2
--without-dbus --without-gnutls --with-rsvg --with-ns
--disable-ns-self-contained'

Configured features:
JPEG RSVG NOTIFY ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message subr-x puny seq byte-opt gv
bytecomp byte-compile cl-extra help-mode cconv cl-loaddefs pcase cl-lib
dired dired-loaddefs format-spec rfc822 mml easymenu mml-sec
password-cache epa derived epg epg-config gnus-util rmail rmail-loaddefs
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils time-date mule-util tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/ns-win ns-win
ucs-normalize term/common-win tool-bar dnd fontset image regexp-opt
fringe tabulated-list newcomment elisp-mode lisp-mode prog-mode register
page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core term/tty-colors frame cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese charscript case-table epa-hook
jka-cmpr-hook help simple abbrev obarray minibuffer cl-preloaded nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote kqueue cocoa ns multi-tty
make-network-process emacs)

Memory information:
((conses 16 206717 18560)
(symbols 48 20249 0)
(miscs 40 75 177)
(strings 32 18166 5363)
(string-bytes 1 584409)
(vectors 16 35204)
(vector-slots 8 670777 6763)
(floats 8 179 123)
(intervals 56 206 0)
(buffers 976 12))