You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="Biocore_2018.jpg|4690" />
  </query-continue>
  <query>
    <pages>
      <page pageid="3423" ns="0" title="CRG User Committee" />
      <page pageid="3985" ns="0" title="Requests statistics in 2015" />
      <page pageid="4263" ns="0" title="BIST Introduction to Statistics 2016" />
      <page pageid="4537" ns="0" title="Projects" />
      <page pageid="4538" ns="0" title="ProjectsBlocks" />
      <page pageid="4696" ns="0" title="CRG PhD &amp; Masters Course 2016 Introduction to Statistics in R" />
      <page pageid="5016" ns="100" title="Private:KEGG pathview" />
    </pages>
  </query>
</api>