python-shell-make-comint

but when I bring up the python shell using 
elpy-shell-send-region-or-buffer
or 
elpy-shell-switch-to-shell

the python-shell-make-comint was not invoked. 
Any thoughts?

BTW, for using cygwin's environment under Windows Emacs, is cygwin-mount the only solution?
I enabled 
(require 'cygwin-mount)
(cygwin-mount-activate)
in my .emacs, and the previous set up of using cygwin64/bin/bash as shell works.

Thanks.

Da 

Date: Sat, 04 Apr 2015 21:44:10 +0300
From: Eli Zaretskii <eliz@gnu.org>
Cc: 20237@debbugs.gnu.org

Date: Sat, 04 Apr 2015 21:38:21 +0300
From: Eli Zaretskii <eliz@gnu.org>
Cc: 20237@debbugs.gnu.org

I think you need to use this instead:

  (setq python-shell-interpreter "/cygdrive/C/Python27/Scripts/ipython")

Or something like that -- I don't use Cygwin, so I might be mistaken
about the exact format you need to use.

Actually, if you use this format, you'd probably also need to use
cygwin-mount as well.

There's probably one more issue here, and maybe this is the root cause
of the problem.  This part of the backtrace you posted:

  make-comint-in-buffer("Python" "*Python*" "c\\:/Python27/Scripts/ipython.exe" nil "-i" "--profile=dev" "--colors=Linux")
  apply(make-comint-in-buffer "Python" "*Python*" "c\\:/Python27/Scripts/ipython.exe" nil ("-i" "--profile=dev" "--colors=Linux"))
  python-shell-make-comint("c\\:/Python27/Scripts/ipython.exe -i --profile=dev --colors=Linux" "Python" nil)
  run-python("c\\:/Python27/Scripts/ipython.exe -i --profile=dev --colors=Linux")

seems to indicate that split-string-and-unquote, called by
python-shell-make-comint, fails to remove the backslash before the
colon.  I don't understand why this happens.  Can you see what's going
on inside python-shell-make-comint?

Fabián, can you help us out here?