URLs in the HTML content are not properly replaced and return a 404

[fnicollet]

Content returned by the PISTE servers look like:

<div id="frontal">

  <link type="text/css" rel="stylesheet" href="https://static.piste.gouv.fr:443/captchEtat/css/bdc-layout-stylesheet.css" />
  <div class="BDC_CaptchaDiv " id="captchaFR_CaptchaDiv" style="width: 280px !important; height: 75px !important; "><!--
 --><div class="BDC_CaptchaImageDiv" id="captchaFR_CaptchaImageDiv" style="width: 250px !important; height: 75px !important;"><!--
   --><img class="BDC_CaptchaImage" id="captchaFR_CaptchaImage" src="/api/simple-captcha-endpoint?get=image&amp;c=captchaFR&amp;t=757eea682fb24b098bdcb6ff49a795ac" alt="Recopier le code de sécurité de cette image" style="visibility: hidden !important" /><!--
 --></div><!--
 --><div class="BDC_CaptchaIconsDiv" id="captchaFR_CaptchaIconsDiv" style="width: 24px !important;"><!--
   --><a class="BDC_ReloadLink" id="captchaFR_ReloadLink" role="button" tabindex="0" href="#" title="Générer un nouveau captcha"><img class="BDC_ReloadIcon" id="captchaFR_ReloadIcon" src="https://static.piste.gouv.fr:443/captchEtat/images/bdc-reload-icon.gif" alt="Générer un nouveau captcha" /></a><!--
   --><a rel="nofollow" class="BDC_SoundLink" id="captchaFR_SoundLink" role="button" tabindex="0" href="/api/simple-captcha-endpoint?get=sound&amp;c=captchaFR&amp;t=xxxxxxxxxxxxxxxxxxxxxxxxx" title="Énoncer le code du captcha"><img class="BDC_SoundIcon" id="captchaFR_SoundIcon" src="https://static.piste.gouv.fr:443/captchEtat/images/bdc-sound-icon.gif" alt="Énoncer le code du captcha" /></a><!--
   --><div class="BDC_Placeholder" id="captchaFR_AudioPlaceholder">&amp;nbsp;</div><!-- --></div>
   <script src="/api/simple-captcha-endpoint?get=script-include&amp;c=captchaFR&amp;t=xxxxxxxxxxxxxxxxxxx" type="text/javascript"></script>
   <input type="hidden" id="BDC_VCID_captchaFR" name="BDC_VCID_captchaFR" value="xxxxxxxxxxxxxxxxx" />
   <input type="hidden" id="BDC_BackWorkaround_captchaFR" name="BDC_BackWorkaround_captchaFR" value="0" />
   <input type="hidden" id="BDC_Hs_captchaFR" name="BDC_Hs_captchaFR" value="xxxxxxxxxxxxxxxxx" />
   <input type="hidden" id="BDC_SP_captchaFR" name="BDC_SP_captchaFR" value="xxxxxxxxxxxx" />

  </div>
</div>

URLs starting with "/api/simple-captcha-endpoint" to not get replaced and end up 404 (unless you magically have an endpoints which matches).
Not sure if this code actually tries to replace those URLs, but it doesn't work:
https://github.com/captcha-com/jquery-captcha/blob/master/src/jquery-captcha.js#L153