Merge branch '76.deploy-key-decoding' into 'develop'

Use a new variable which actually holds a path

Closes #76

See merge request !136

.gitlab-ci.yml

@@ -90,10 +90,13 @@ system-tests:
       # Make up a safe-ish place on the filesystem to write the key.
       KEY_PATH="$(mktemp -d)/deploy_key"
 
-      # The environment variable holding the key is configured with GitLab
-      # using Terraform so we can retain some bare minimum level of
-      # confidentiality.
-      base64 --decode "${PRIVATESTORAGEIO_STAGING_SSH_DEPLOY_KEY}" > "${KEY_PATH}"
+      # The environment variable holding the path to the key is configured
+      # with GitLab using Terraform so we can retain some bare minimum level
+      # of confidentiality.
+      #
+      # It contains the *path to the key*.  It does not contain the key
+      # itself.
+      base64 --decode "${PRIVATESTORAGEIO_SSH_DEPLOY_KEY_PATH}" > "${KEY_PATH}"
 
     # Update the deployment
     - |