Handling exception on cache_key_salt on site update

ee/cli/plugins/site.py

@@ -1307,6 +1307,9 @@ class EESiteUpdateController(CementBaseController):
         if oldcachetype != 'wpredis' and data['wpredis']:
             try:
                 if installwp_plugin(self, 'redis-cache', data):
+                    if EEShellExec.cmd_exec(self, "grep -r \"WP_CACHE_KEY_SALT\" {0}/wp-config.php".format(ee_site_webroot)):
+                        pass
+                    else:
                         try:
                             wpconfig = open("{0}/wp-config.php".format(ee_site_webroot),
                                                encoding='utf-8', mode='a')