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

[Jean Felder <jfelder src gnome org>]

commit de8b727458067aedec9d156a3b3aad44cee1b345
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 | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 88b15236..3fc511e8 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -15,7 +15,7 @@ variables:
 flatpak:
   stage: build-flatpak
   script:
-    - flatpak-builder --stop-at=${FLATPAK_MODULE} app ${MANIFEST_PATH}
+    - flatpak-builder --user --disable-rofiles-fuse --stop-at=${FLATPAK_MODULE} app ${MANIFEST_PATH}
     - flatpak build app meson --prefix=/app _build
     - flatpak build app ninja -C _build install
     - flatpak-builder --finish-only --repo=repo app ${MANIFEST_PATH}
@@ -60,6 +60,7 @@ stop_review:
         - tags
 
 flake8:
+  image: fedora:28
   stage: check
   script:
     - dnf install -y python3-flake8