bug#20237: Emacs built on Windows cannot figure out path correctly

[Eli Zaretskii]

> Date: Sat, 04 Apr 2015 14:18:56 -0400
> From: Da Zhang <zhangda82@gmail.com>
> CC: 20237@debbugs.gnu.org
> 
> Thanks for  your time!
> 
> M-: (w32-shell-name) RET returns
> 
> "C:/cygwin64/bin/bash.exe"

OK, I think the situation is clear now: you have set up Emacs for
using the Cygwin Bash as the shell, but the value of
python-shell-interpreter is not in the Cygwin-compatible format.  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.

Alternatively, remove your customizations that cause w32-shell-name
return the Cygwin Bash shell.  It could come from either setting the
value of shell-file-name in your init files, or from the SHELL or
ESHELL environment variable defined outside Emacs.

Thanks.