Template module failing when using su

[John Doe]

Hello,

I found an error in deploying a file through template module when using su. It stops with error message: "Source /tmp/ansible-tmp-1407982491.27-242988883727372/source not readable."
When I checked permission on that file I saw that it was 600:

-bash-3.2$ ls -lR ansible*
ansible-tmp-1407982491.27-242988883727372:
total 128
-rw-r--r--   1 johndoe    other      61318 Aug 14 09:14 copy
-rw-------   1 johndoe    other        220 Aug 14 09:14 source
-bash-3.2$

I wonder if anybody have similar problem or maybe you have any ideas what can cause this error?   

NB. Just in case: "copy" module works fine; I've tried to use Solaris and Linux as managed OS, the result was same.

PS. I've sent a bug report, and attached all details about the problem. Here is the link: https://github.com/ansible/ansible/issues/8594

Here is the playbook:

- name: Template fails as su
  hosts: all
  vars:
    user_name: appadm

  tasks:
    - name: Create some configuration file
      su: yes
      su_user: "{{ user_name }}"
      template: src=config dest=/tmp/config

--
Regards,
  John