[gnome-music/wip/jfelder/3-34-unprivileged-ci] CI: Update to run as unprivileged

[Jean Felder <jfelder src gnome org>]

commit d1f9f190adff455a816949e5f8e584b352a6654e
Author: Jean Felder <jfelder src gnome org>
Date:   Fri Feb 21 11:55:30 2020 +0100

    CI: Update to run as unprivileged
    
    There is no default image for the runner. An image needs to be
    specified in order to install flake8.

 .gitlab-ci.yml | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 88b15236..7362382a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -60,6 +60,7 @@ stop_review:
         - tags
 
 flake8:
+  image: fedora:28
   stage: check
   script:
     - dnf install -y python3-flake8