[O] async export not working for me

[Julien Cubizolles]

I'm running org-mode 8.3beta from org-plus-contrib in melpa. I must have
missed something obvious cause I could never get async export working.

Here is what I do:
--8<---------------cut here---------------start------------->8---
emacs -Q
(require 'package)
(package-initialize) ;; since org is installed by package
--8<---------------cut here---------------end--------------->8---


create a test.org file with only

--8<---------------cut here---------------start------------->8---
* First Heading
* Second Heading
--8<---------------cut here---------------end--------------->8---

run 

--8<---------------cut here---------------start------------->8---
C-c
C-a ;; in the export dispatcher
l
p
--8<---------------cut here---------------end--------------->8---

I get:

--8<---------------cut here---------------start------------->8---
Initializing asynchronous export process
org-export-to-file: Wrong type argument: stringp, nil
--8<---------------cut here---------------end--------------->8---

the synchronous export works fine.

If I run emacs with my regular config files, I get:
--8<---------------cut here---------------start------------->8---
Initializing asynchronous export process
Process 'org-export-process' exited abnormally
--8<---------------cut here---------------end--------------->8---

different error message but still not ok.

What could possibly go wrong ?

Julien.