Adding debian to CI to test python 3.5.

Solves #40.

.gitlab-ci.yml

@@ -11,12 +11,11 @@ before_script:
   - export PATH=~/.local/bin:${PATH}
   - pip3 install --user -e .
 
-tests-fedora:
+.linux-tests-template: &linux-tests
   stage: test
   variables:
     PYTEST_ADDOPTS: "--color=yes"
   script:
-    - yum -y install clang libffi-devel openssl-devel python3-devel
     - python3 setup.py test
     - mkdir -p coverage/
     - cp .coverage.* coverage/coverage."${CI_JOB_NAME}"
@@ -24,6 +23,14 @@ tests-fedora:
     paths:
     - coverage/
 
+tests-debian:
+  image: buildstream/buildstream-debian
+  <<: *linux-tests
+
+tests-fedora:
+  script:
+    - yum -y install clang libffi-devel openssl-devel python3-devel
+  <<: *linux-tests
 
 tests-dummy-job-fedora:
   stage: test