fix: var type

.gitlab-ci.yml

@@ -6,7 +6,7 @@ default:
 # only cache local items.
 variables:
   PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache/pip"
-  CI_DEBUG_TRACE: true
+  CI_DEBUG_TRACE: "true"
 
 # Pip's cache doesn't store the python packages
 # https://pip.pypa.io/en/stable/reference/pip_install/#caching