python.el: Support interpreter paths with spaces

Fixes: debbugs:19289

* lisp/progmodes/python.el (python-shell-parse-command): Quote
`python-shell-interpreter`.

lisp/ChangeLog

+2014-12-09  Fabián Ezequiel Gallina  <fgallina@gnu.org>
+
+	* progmodes/python.el (python-shell-parse-command): Quote
+	`python-shell-interpreter`.  (Bug#19289)
+
 2014-12-04  Stefan Monnier  <monnier@iro.umontreal.ca>
 
 	* progmodes/sh-script.el (sh-smie-sh-rules): Go back to the beginning

lisp/progmodes/python.el

@@ -2086,7 +2086,8 @@ uniqueness for different types of configurations."
         (exec-path (python-shell-calculate-exec-path)))
     (format "%s %s"
             ;; FIXME: Why executable-find?
-            (executable-find python-shell-interpreter)
+            (shell-quote-argument
+             (executable-find python-shell-interpreter))
             python-shell-interpreter-args)))
 
 (defun python-shell-calculate-process-environment ()