Update .gitlab-ci.yml to python 3.6

.gitlab-ci.yml

@@ -4,11 +4,11 @@ pages:
     - yum install -y epel-release wget
     - wget https://repo.ius.io/ius-release-el7.rpm
     - rpm -Uvh ius-release-*.rpm
-    - yum provides python3.5
-    - yum install -y python35u python35u-libs python35u-devel python35u-pip
-    - pip3.5 install -U pip
-    - pip3.5 install virtualenv
-    - virtualenv -p python3.5 venv
+    - yum provides python3.6
+    - yum install -y python36u python36u-libs python36u-devel python36u-pip
+    - pip3.6 install -U pip
+    - pip3.6 install virtualenv
+    - virtualenv -p python3.6 venv
     - . venv/bin/activate
     - pip3 install sphinx
     - yum install -y make