babel: Handle errors when temporary directory is on a different partition

* lisp/ob.el (org-babel-remove-temporary-directory): Handle exception
  with message informing of failure to remove directory.

Thanks to Antti Kaihola for the bug report:

http://thread.gmane.org/gmane.emacs.orgmode/34394

From: Antti Kaihola <akaihola <at> gmail.com>
Subject: Can't close Emacs+org-mode if /tmp and /home on different	partitions
Newsgroups: gmane.emacs.orgmode
Date: 2010-12-02 08:33:28 GMT (6 days, 1 hour and 22 minutes ago)
I have /tmp on my root partition and a separate partition for /home.
When trying to close an Emacs session which is using org-mode, I get
this error:

    move-file-to-trash: Non-regular file: Is a directory, /tmp/babel-XXXXXXX

(where XXXXXXX are random characters).

I tracked down the problem to org-babel-remove-temporary-directory
which ob.el adds to kill-emacs-hook. It tries to remove the temporary
directory using delete-directory, which in turn tries to move the
directory (by renaming) into trash, which is in my home directory.

I added this to my ~/.emacs.d/init.el:

   (custom-set-variables '(temporary-file-directory "/home/akaihola/tmp/"))

and closing Emacs works correctly again. However, since my init.el is
part of emacs-starter-kit which I update frequently, I'd prefer not to
modify that file. Unfortunately the customization hook
emacs-starter-kit provides (~/.emacs.d/custom.el) is loaded too late
to affect the temporary directory.

I'm running emacs-snapshot 1:20090909-1 in Ubuntu 10.10. Looks like
this is really an Emacs bug and is already fixed:
http://groups.google.com/group/gnu.emacs.bug/browse_thread/thread/0446b8684a8ef504

lisp/ob.el

@@ -1942,17 +1942,22 @@ of `org-babel-temporary-directory'."
   (when (and (boundp 'org-babel-temporary-directory)
 	     (file-exists-p org-babel-temporary-directory))
     ;; taken from `delete-directory' in files.el
-    (mapc (lambda (file)
-	    ;; This test is equivalent to
-	    ;; (and (file-directory-p fn) (not (file-symlink-p fn)))
-	    ;; but more efficient
-	    (if (eq t (car (file-attributes file)))
-		(delete-directory file)
-	      (delete-file file)))
-	  ;; We do not want to delete "." and "..".
-	  (directory-files org-babel-temporary-directory 'full
-			   "^\\([^.]\\|\\.\\([^.]\\|\\..\\)\\).*"))
-    (delete-directory org-babel-temporary-directory)))
+    (condition-case nil
+	(progn
+	  (mapc (lambda (file)
+		  ;; This test is equivalent to
+		  ;; (and (file-directory-p fn) (not (file-symlink-p fn)))
+		  ;; but more efficient
+		  (if (eq t (car (file-attributes file)))
+		      (delete-directory file)
+		    (delete-file file)))
+		;; We do not want to delete "." and "..".
+		(directory-files org-babel-temporary-directory 'full
+				 "^\\([^.]\\|\\.\\([^.]\\|\\..\\)\\).*"))
+	  (delete-directory org-babel-temporary-directory))
+      (error
+       (message "Failed to remove temporary Org-babel directory %s"
+		org-babel-temporary-directory)))))
 
 (add-hook 'kill-emacs-hook 'org-babel-remove-temporary-directory)