fix ci

.gitlab-ci.yml

@@ -15,7 +15,7 @@ build:
   stage: build
   script:
     - apt-get install -y --force-yes build-essential python-dev python-pip git nodejs nodejs-legacy npm
-    - pip install --upgrade pip
+    - pip install --upgrade pip==9.0.3
     - pip install --editable .
     - cd content && npm install && cd ..
     - sed -i "s/RELATIVE_URLS = True/RELATIVE_URLS = False/" pelicanconf.py