[gimp/wip/Jehan/CI-Windows] Add rst2man deps.

[Jehan <jehanp src gnome org>]

commit 8ce9fc177b65080635fe655d7a16c83602df5048
Author: Jehan <jehan girinstud io>
Date:   Wed Sep 25 16:17:47 2019 +0200

    Add rst2man deps.

 .gitlab-ci.yml | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 85f93c4cdf..33536f6b0b 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -34,6 +34,7 @@ cache:
     - pacman -Syu --noconfirm --needed --cachedir "${PACMAN_CACHE}"
         git
         base-devel
+        python-docutils
         python-pip
     - pip3 install --user crossroad