Make gradle installation fail in a friendlier way on CentOS

roles/matrix-mxisd/tasks/setup_mxisd.yml

@@ -25,23 +25,28 @@
     force: "{{ omit if ansible_version.major > 2 or ansible_version.minor >= 8 else matrix_mxisd_docker_image_force_pull }}"
   when: matrix_mxisd_enabled|bool and not matrix_mxisd_container_image_self_build
 
-- name: Ensure gradel is installed for self-building
+- block:
+  - name: Ensure gradle is installed for self-building
     apt:
       name:
         - gradle
       state: present
       update_cache: yes
-  when: "matrix_mxisd_enabled|bool and matrix_mxisd_container_image_self_build"
+    when: (ansible_os_family == 'Debian')
 
-- name: Ensure mxisd repository is present on self-build
+  - name: Ensure gradle is installed for self-building
+    fail:
+      msg: "Installing gradle on CentOS is currently not supported, so self-building mxisd cannot happen at this time"
+    when: ansible_distribution == 'CentOS'
+
+  - name: Ensure mxisd repository is present on self-build
     git:
       repo: https://github.com/kamax-matrix/mxisd.git
       dest: "{{ matrix_mxisd_docker_src_files_path }}"
       version: "v{{ matrix_mxisd_docker_image.split(':')[1] }}"
       force: "yes"
-  when: "matrix_mxisd_enabled|bool and matrix_mxisd_container_image_self_build"
 
-- name: Ensure mxisd Docker image is build
+  - name: Ensure mxisd Docker image is built
     shell: "./gradlew dockerBuild"
     args:
       chdir: "{{ matrix_mxisd_docker_src_files_path }}"