install: verify that at least one master is schedulable

roles/openshift_sanitize_inventory/tasks/main.yml

@@ -115,3 +115,15 @@
   when:
     - openshift_master_console_port is defined
     - openshift_master_console_port != openshift_master_api_port
+
+- name: At least one master is schedulable
+  fail:
+    msg: >
+      No schedulable masters found, please remove 'openshift_schedulable=False' from all of your masters.
+  when:
+    - l_master_schedulable | length > 0
+    - false in l_master_schedulable
+  vars:
+    l_masters_group: "{{ ('oo_masters_to_config' in groups) | ternary('oo_masters_to_config', 'oo_nodes_to_bootstrap') }}"
+    l_openshift_schedulable: "{{ groups[l_masters_group] | map('extract', hostvars, 'openshift_schedulable') | select('defined') | list }}"
+    l_master_schedulable: "{{ l_openshift_schedulable | map('bool') | list }}"