bug#23678: 24.5; Python auto-completion breaks inferior-python mode

[jay malby]

When running a python interpreter in inferior-python mode,
sometimes calling auto-completion with C-M-i on an indented
line causes the underlying python interpreter to get confused,
leading it to produce an unexpected indent error.

Steps to reproduce:
1. Start emacs with a blank config
2. run-python
3. run this code, performing auto-completion (C-M-i) between the "5"
and ":" on line 2:
for i in range(10):
  if  i < 5:
    print(i)

Python will break after hitting enter on the second line, reporting an
unexpected indent. The same code without the C-M-i will run fine,
printing the integers between 0 and 4 (inclusive).



In GNU Emacs 24.5.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.20.3)
 of 2016-05-05 on arojas
Windowing system distributor `The X.Org Foundation', version 11.0.11803000
System Description:    Arch Linux

Configured using:
 `configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --with-x-toolkit=gtk3 --with-xft
 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe
 -fstack-protector-strong' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'

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

Major mode: Inferior Python

Minor modes in effect:
  compilation-shell-minor-mode: t
  tooltip-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
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Starting Emacs daemon.
When done with this frame, type C-x 5 0
Making python-shell-interpreter local to *Python* while let-bound!
Making python-shell-interpreter-args local to *Python* while let-bound!
Sent python-shell-completion-setup-code
Sent python-ffap-setup-code
Sent python-eldoc-setup-code
No match

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message idna format-spec
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util help-fns mail-prsvr mail-utils compile cl-extra python easymenu
json comint ring cl-loaddefs cl-lib ansi-color server time-date tooltip
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
lisp-mode prog-mode register page menu-bar rfn-eshadow timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core frame cham
georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese hebrew greek romanian slovak czech european ethiopic
indian cyrillic chinese case-table epa-hook jka-cmpr-hook help simple
abbrev minibuffer 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 make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 84389 8157)
 (symbols 48 18864 0)
 (miscs 40 56 174)
 (strings 32 13129 4758)
 (string-bytes 1 399070)
 (vectors 16 10809)
 (vector-slots 8 401723 6355)
 (floats 8 73 175)
 (intervals 56 270 0)
 (buffers 960 13)
 (heap 1024 37934 927))