HTML Export will fail when SSX are inside several nested spaces

        // There can be some calls to URLs inside the SSX content. For example:
        //   background-image: url("$xwiki.getSkinFile('icons/silk/folder_add.png')");
        // In order for these URLs to be resolved correctly they need to be relative to where the CSS file is located
        // on disk. Thus we adjust the CSS path by 3 levels since we're locating the SSX files in "ssx/<space>/<page>".
        exportContext.pushCSSParentLevels(3);