Move cache clear for Drush. (#23)

tasks/main.yml

@@ -79,17 +79,23 @@
     mode: 0770
   become: "{{ deploydrupal_files_become }}"
 
-- name: clear drush cache.
-  shell: "{{ deploydrupal_drush_path }} cache-clear drush"
-  args:
-    chdir: "{{ deploydrupal_core_path }}/sites/{{ deploydrupal_site_name }}"
-
 - name: clear caches.
   shell: "{{ deploydrupal_drush_path }} cache-rebuild"
   args:
     chdir: "{{ deploydrupal_core_path }}/sites/{{ deploydrupal_site_name }}"
   when:
     - not deploydrupal_site_install
+    - deploydrupal_drush_cache_rebuild
+
+# Drush ^9 uses the Drupal service container. We intentionally clear the Drupal
+# cache before the Drush cache to avoid fatal errors due to stale cache in the
+# service container.
+- name: clear drush cache.
+  shell: "{{ deploydrupal_drush_path }} cache-clear drush"
+  args:
+    chdir: "{{ deploydrupal_core_path }}/sites/{{ deploydrupal_site_name }}"
+  when:
+    - deploydrupal_drush_cache_rebuild
 
 # site-install.
 - name: install site.