add return value

ee/cli/plugins/site.py

@@ -1306,7 +1306,20 @@ class EESiteUpdateController(CementBaseController):
 
         if oldcachetype != 'wpredis' and data['wpredis']:
             try:
-                installwp_plugin(self, 'redis-cache', data)
+                if installwp_plugin(self, 'redis-cache', data):
+                    try:
+                        wpconfig = open("{0}/wp-config.php".format(ee_site_webroot),
+                                  encoding='utf-8', mode='a')
+                        wpconfig.write("\n\ndefine( \'WP_CACHE_KEY_SALT\', \'{0}:\' );"
+                                     .format(ee_domain))
+                        wpconfig.close()
+                    except IOError as e:
+                        Log.debug(self, str(e))
+                        Log.debug(self, "Editing wp-config.php failed.")
+                        Log.info(self, Log.FAIL + "Editing wp-config failed. "
+                                    "Could not append:"
+                                     " define( 'WP_CACHE_KEY_SALT', '{sitename}:' );")
+
             except SiteError as e:
                 Log.debug(self, str(e))
                 Log.info(self, Log.FAIL + "Update site failed."