Change source repo.

.gitlab-ci.yml

@@ -9,10 +9,10 @@ before_script:
     - which python
     - which pip
     - python --version
-    - DEBIAN_FRONTEND=noninteractive apt-get install -yq python3.6
+    - DEBIAN_FRONTEND=noninteractive apt-get -t jessie install -yq python3.6
 
-    - apt-get -t testing install -y -qq python3-pip
-    - apt-get -t testing install -y -qq python3-pytest
+    - apt-get -t jessie install -y -qq python3-pip
+    - apt-get -t jessie install -y -qq python3-pytest
 
     - pip3 install https://gitlab.mpcdf.mpg.de/ievo/ctapipe-mpp/-/archive/master/ctapipe-mpp-master.tar.gz
     - pip3 install https://github.com/cta-observatory/ctapipe-extra/archive/master.tar.gz