use python3.5 on ansible worker to deploy webserver

because ansible does not support python3.4 anymore, and this 
causes this on deployment:
https://github.com/ansible/ansible/issues/24180
Former-commit-id: 5448751bd777f3f2d9b60dea313cf8fa2305fedc

.gitlab-ci.yml

@@ -28,7 +28,9 @@ deploy-webserver:
   script:
     - yum install -y epel-release
     - yum install -y gcc
-    - yum install -y python34-pip python34-devel
+    - wget https://centos7.iuscommunity.org/ius-release.rpm
+    - rpm -Uvh ius-release*.rpm
+    - yum install -y python35u python35u-libs python35u-devel python35u-pip
     - pip3 install ansible
     - cd ansible
     - whoami