bug#25753: 25.2; Python mode shell interaction not working 100%

[charles@aurox.ch (Charles A. Roelli)]

In emacs 25.2 (rc1) and 25.1, interaction with the Python shell does not
seem to be working fully.  Python version is '2.7.12 (v2.7.12:d33e0cf91556,
Jun 26 2016, 12:10:39) [GCC 4.2.1 (Apple Inc. build 5666) (dot 3)]', and
this is on Snow Leopard.

- emacs -Q
- open any Python file
- M-x run-python, and this pops up:

  Warning (python): Your ‘python-shell-interpreter’ doesn’t seem to
  support readline, yet ‘python-shell-completion-native’ was t and
  "python" is not part of the
  ‘python-shell-completion-native-disabled-interpreters’ list.  Native
  completions have been disabled locally.
  
  [and yet `import readline, rlcompleter' works fine for me]

- quit that warning, and the *Python* shell states "python.el: native
  completion setup loaded".
- test out completion in the shell, it seems to be working okay
  (`import sys RET sys . TAB' shows the attributes of `sys').  Not sure
  if this is `native' completion though.
- switch to the Python file.  Place point over a module, global
  variable, function, or function definition, and this pops up in the
  echo area (meant to be eldoc documentation, I think):

  import codecs, os;
  __pyfile = codecs.open('''/var/folders/WP/WPe0Q1iAGc0J7iI6J50jcU+++TI/-Tmp-/py1883fcQ''',encoding='''utf-8''');
  __code = __pyfile.read().encode('''utf-8''');
  __pyfile.close();
  os.remove('''/var/folders/WP/WPe0Q1iAGc0J7iI6J50jcU+++TI/-Tmp-/py1883fcQ''');
  exec(compile(__code,'''/path/to/python/buffer/here''','exec'));
  
  [some line breaks included for readability]

  The same sort of thing is returned by calling, say,
  `(python-ffap-module-path "twisted")'.  Any pointers on fixing this?




In GNU Emacs 25.2.1 (x86_64-apple-darwin10.8.0, NS appkit-1038.36 Version 10.6.8 (Build 10K549))
 of 2017-02-07 built on gray
Windowing system distributor 'Apple', version 10.3.1038
Configured using:
 'configure --with-modules'

Configured features:
JPEG RSVG NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS MODULES