[gnome-build-meta/tristan/cargo-source-plugin] .gitlab-ci.yml: Give us pytoml in CI for our cargo plugin

[Tristan Van Berkom <tvb src gnome org>]

commit 924be839cb450049652693c25f7c9c1dc4ed0479
Author: Tristan Van Berkom <tristan vanberkom codethink co uk>
Date:   Mon Jul 29 15:30:03 2019 -0400

    .gitlab-ci.yml: Give us pytoml in CI for our cargo plugin

 .gitlab-ci.yml | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 2de59951..bb50da11 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -25,6 +25,10 @@ stages:
 
 default:
   before_script:
+
+  # Install pytoml for our plugin
+  - pip3 install pytoml
+
   # Use specific version of BuildStream
   - git clone https://gitlab.com/BuildStream/buildstream.git
   - git -C buildstream/ checkout $BST_SHA