Zend certified PHP/Magento developer

Maintance Mode: How to show the content of my 503.phtml page istead of exceptions

1 exception(s):
Exception #0 (Exception): Unable to proceed: the maintenance mode is enabled. 

Exception #0 (Exception): Unable to proceed: the maintenance mode is enabled. 
<pre>#1 MagentoFrameworkAppBootstrap->run() called at [pub/index.php:31]
</pre>