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="EI_GUI.PNG" />
  </query-continue>
  <query>
    <pages>
      <page pageid="94" ns="6" title="File:B A BA de l ANOVA 151117.pdf" />
      <page pageid="253" ns="6" title="File:Bandeau logos.png" />
      <page pageid="150" ns="6" title="File:Banner EPJB2017.jpg" />
      <page pageid="85" ns="6" title="File:CapteurBruit1.png" />
      <page pageid="86" ns="6" title="File:CapteurBruit2.png" />
      <page pageid="254" ns="6" title="File:Capteur OPM.png" />
      <page pageid="126" ns="6" title="File:ChristianBénar CV eng.pdf" />
      <page pageid="111" ns="6" title="File:Cooc splash.png" />
      <page pageid="241" ns="6" title="File:Cpp.png" />
      <page pageid="236" ns="6" title="File:Delphos.png" />
    </pages>
  </query>
</api>