puts a dash alert on all sites when activated network wide

dashalert.php

<?php 
/*
Plugin Name: Dash Alert
Plugin URI: https://gist.github.com/woodwardtw/683e8ba3d53a56607f112cb1d29fda26
Description:  a dashboard alert
Author: Tom
Version: 0.1
Author URI: http://bionicteaching.com/
*/
function my_admin_notice(){
    echo '<div class="updated" style="background-color: yellow; border-left: 5px solid red">
    <img src="http://altlab.vcu.edu/wp-content/uploads/2014/07/ALT-Lab-logo-color1.png" style="float:left; padding: 5px;">
       <h2>Rampages will be undergoing an upgrade from 11:00PM EDT Saturday, Sept. 10 until 7:00AM Sunday, Sept. 11.</h2> <p>We will be upgrading infrastructure and making other improvements to deal with our continued growth. No rampages.us content will be accessible during this time. </p><p>Should you have any questions or concerns please contact <a href="mailto:altlab@vcu.edu">altlab@vcu.edu</a>.</p></div>';
}
add_action('admin_notices', 'my_admin_notice');