Force Python Docker version for Travis.

WIP

WIP

.travis.yml

@@ -1,35 +1,37 @@
 ---
-language: python
-services: docker
+  language: python
+  services: docker
+  
+  env:
+    global:
+      - ROLE_NAME: cloudflare-acme
+    matrix:
+      - MOLECULE_DISTRO: centos7
+      - MOLECULE_DISTRO: centos8
+      - MOLECULE_DISTRO: ubuntu1804
+      - MOLECULE_DISTRO: ubuntu1604
+      - MOLECULE_DISTRO: debian9
+      - MOLECULE_DISTRO: debian10
 
-env:
-  global:
-    - ROLE_NAME: cloudflare-acme
-  matrix:
-    - MOLECULE_DISTRO: centos7
-    - MOLECULE_DISTRO: centos8
-    - MOLECULE_DISTRO: ubuntu1804
-    - MOLECULE_DISTRO: ubuntu1604
-    - MOLECULE_DISTRO: debian9
-    - MOLECULE_DISTRO: debian10
-
-install:
-  # Install test dependencies.
-  - pip install molecule docker testinfra ansible-lint flake8 yamllint
-
-before_script:
-  # Use actual Ansible Galaxy role name for the project directory.
-  - cd ../
-  - mv ansible-$ROLE_NAME $ROLE_NAME
-  - cd $ROLE_NAME
-
-script:
-  - molecule --version
-  - ansible --version
-  - molecule test
-
-notifications:
-  webhooks:
-    urls:
-      - "https://galaxy.ansible.com/api/v1/notifications/"
-    on_success: change
+  install:
+    # Install test dependencies.
+    - pip install molecule docker==4.2.2 testinfra ansible-lint flake8 yamllint
+  
+  before_script:
+    # Use actual Ansible Galaxy role name for the project directory.
+    - cd ../
+    - mv ansible-$ROLE_NAME $ROLE_NAME
+    - cd $ROLE_NAME
+  
+  script:
+    - docker --version
+    - molecule --version
+    - ansible --version
+    - molecule test
+  
+  notifications:
+    webhooks:
+      urls:
+        - "https://galaxy.ansible.com/api/v1/notifications/"
+      on_success: change
+