Install python-pylibmc in the test env

.gitlab-ci.yml

@@ -8,7 +8,7 @@ run_tests:
   stage: test
   image: "ai/test:base"
   script:
-    - "apt-get install -q -y autoconf automake libtool libcurl4-openssl-dev libpam0g-dev"
+    - "apt-get install -q -y autoconf automake libtool libcurl4-openssl-dev libpam0g-dev python-pylibmc"
     - "(cd pam && ./autogen.sh && ./configure && make)"
     - "tox -e py27"