Run migrate on every DB in DATABASES for both lms and the cms

Does so by running the edxapp role just to generate config (as
controlled by check-migrations.sh's use of the --tag) and then
the tasks in the playbook are hardcoded to always run, regardless
of the tag.  Because the edxapp play has run, the tasks have
access to the various config variables containing DATABASES
and can tell what DBs are in use.

Skip the read replica

playbooks/edx-east/edxapp_migrate.yml

@@ -4,14 +4,32 @@
   gather_facts: False
   vars:
     db_dry_run: "--list"
+  roles:
+    - edxapp
   tasks:
-    - name: migrate
+    - name: migrate lms
       shell: >
         chdir={{ edxapp_code_dir }}
-        python manage.py {{ item }} migrate --noinput {{ db_dry_run }} --settings=aws_migrate
+        python manage.py lms migrate --database {{ item }} --noinput {{ db_dry_run }} --settings=aws_migrate
       environment:
         DB_MIGRATION_USER: "{{ COMMON_MYSQL_MIGRATE_USER }}"
         DB_MIGRATION_PASS: "{{ COMMON_MYSQL_MIGRATE_PASS }}"
+      # Migrate any database in the config, but not the read_replica
+      when: item != 'read_replica'
       with_items:
-        - lms
-        - cms
+        - "{{ lms_auth_config.DATABASES.keys() }}"
+      tags:
+        - always
+    - name: migrate cms
+      shell: >
+        chdir={{ edxapp_code_dir }}
+        python manage.py cms migrate --database {{ item }} --noinput {{ db_dry_run }} --settings=aws_migrate
+      environment:
+        DB_MIGRATION_USER: "{{ COMMON_MYSQL_MIGRATE_USER }}"
+        DB_MIGRATION_PASS: "{{ COMMON_MYSQL_MIGRATE_PASS }}"
+      # Migrate any database in the config, but not the read_replica
+      when: item != 'read_replica'
+      with_items:
+        - "{{ cms_auth_config.DATABASES.keys() }}"
+      tags:
+        - always

util/jenkins/check-migrations.sh

@@ -58,13 +58,12 @@ extra_var_args+=" -e edxapp_code_dir=${WORKSPACE}/edx-platform"
 extra_var_args+=" -e edxapp_user=jenkins"
 extra_var_args+=" -e EDXAPP_CFG_DIR=${WORKSPACE}"
 
-# Generate the json configuration files
-ansible-playbook -c local $extra_var_args --tags edxapp_cfg -i localhost, -s -U jenkins edxapp.yml
-
 # Run migrations and replace literal '\n' with actual newlines to make the output
 # easier to read
+# We use the edxapp_cfg tag so that the edxapp role will generate config files but
+# nothing else.  The actual migrate commands are then run from the playbook.
 
-ansible-playbook -v -c local $extra_var_args -i localhost, -s -U jenkins edxapp_migrate.yml | sed 's/\\n/\n/g'
+ansible-playbook -v -c local $extra_var_args --tags edxapp_cfg -i localhost, -s -U jenkins edxapp_migrate.yml | sed 's/\\n/\n/g'
 
 #We don't care about the exit status of the `sed`
 exit ${PIPESTATUS[0]}