TypeError: can't serialize Undefined

; line 25

---
[...]
    - name: {{ patches_done_dir }}
    - user: root
    - group: root
    - mode: 755

{%- for full_file in salt['cp.list_master'](saltenv=salt.environment, prefix=patches_source) -%}    <======================
  {%- set file = full_file|replace(patches_source ~ '/', '') -%}
  {%- set done_file = grains.get('saltversion', 'unknown') ~ '_' ~ file|replace('/', '_') %}
{{ full_file }}:
  cmd.run:
    - cwd: '/usr/lib/python2.7/dist-packages/salt'
[...]
---