check ansible version for self-building in every role

roles/matrix-synapse/tasks/init.yml

@@ -5,3 +5,10 @@
 - set_fact:
     matrix_systemd_services_list: "{{ matrix_systemd_services_list + ['matrix-goofys'] }}"
   when: matrix_s3_media_store_enabled|bool
+
+# ansible lower than 2.8, does not support docker_image build parameters
+# for self buildig it is explicitly needed, so we rather fail here
+- name: Fail if running on Ansible lower than 2.8 and trying self building
+  fail:
+    msg: "To self build Synapse image, you should usa ansible 2.8 or higher. E.g. pip contains such packages."
+  when: "ansible_version.major == 2 and ansible_version.minor < 8 and matrix_synapse_self_build"