Remove sudo requirement from Travis build.

.travis.yml

@@ -1,50 +1,38 @@
 ---
-sudo: required
+services: docker
 
 env:
-  global:
-    # https://github.com/travis-ci/travis-ci/issues/6461#issuecomment-239577306
-    DOCKER_VERSION: "1.9.1-0~trusty"
-  matrix:
-    - distro: centos7
-      init: /usr/lib/systemd/systemd
-      run_opts: "--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
-    - distro: ubuntu1604
-      init: /lib/systemd/systemd
-      run_opts: "--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
-    - distro: ubuntu1404
-      init: /sbin/init
-      run_opts: ""
-    - distro: ubuntu1204
-      init: /sbin/init
-      run_opts: ""
-
-services:
-  - docker
+  - distro: centos7
+    init: /usr/lib/systemd/systemd
+    run_opts: "--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
+  - distro: ubuntu1604
+    init: /lib/systemd/systemd
+    run_opts: "--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
+  - distro: ubuntu1404
+    init: /sbin/init
+    run_opts: ""
+  - distro: ubuntu1204
+    init: /sbin/init
+    run_opts: ""
 
 before_install:
-  # Downgrade to older version of Docker engine.
-  - sudo apt-get update
-  - sudo apt-get remove docker-engine -yq
-  - sudo apt-get install docker-engine=$DOCKER_VERSION -yq --no-install-suggests --no-install-recommends --force-yes -o Dpkg::Options::="--force-confnew"
-
   # Pull container.
-  - 'sudo docker pull geerlingguy/docker-${distro}-ansible:latest'
+  - 'docker pull geerlingguy/docker-${distro}-ansible:latest'
 
 script:
   - container_id=$(mktemp)
   # Run container in detached state.
-  - 'sudo docker run --detach --volume="${PWD}":/etc/ansible/roles/role_under_test:ro ${run_opts} geerlingguy/docker-${distro}-ansible:latest "${init}" > "${container_id}"'
+  - 'docker run --detach --volume="${PWD}":/etc/ansible/roles/role_under_test:ro ${run_opts} geerlingguy/docker-${distro}-ansible:latest "${init}" > "${container_id}"'
 
   # Ansible syntax check.
-  - 'sudo docker exec --tty "$(cat ${container_id})" env TERM=xterm ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml --syntax-check'
+  - 'docker exec --tty "$(cat ${container_id})" env TERM=xterm ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml --syntax-check'
 
   # Test role.
-  - 'sudo docker exec --tty "$(cat ${container_id})" env TERM=xterm ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml'
+  - 'docker exec "$(cat ${container_id})" ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml'
 
   # Test role idempotence.
   - idempotence=$(mktemp)
-  - sudo docker exec "$(cat ${container_id})" ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml | tee -a ${idempotence}
+  - docker exec "$(cat ${container_id})" ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml | tee -a ${idempotence}
   - >
     tail ${idempotence}
     | grep -q 'changed=0.*failed=0'
@@ -54,9 +42,5 @@ script:
   # Check if nginx is running.
   # TODO
 
-after_success:
-  # Clean up.
-  - 'sudo docker stop "$(cat ${container_id})"'
-
 notifications:
   webhooks: https://galaxy.ansible.com/api/v1/notifications/