'Alt' attributes not detected for links that contain images

AFFECTS:

• All pages
• xwiki:XWiki.WatchListRss
• xwiki:Main.WebHome
• etc.

ERROR:

• org.xwiki.test.webstandards.CustomDutchWebGuidelinesValidationTest.Validating HTML5 Dutch Web Guidelines validity for: xwiki:XWiki.WatchListRss executed with credentials Admin:admin (from org.xwiki.test.webstandards.AllTests)
• ERROR: At least one link contains only an image without a correct alt attribute (not empty), links can contain img with an empty attribute only if it also contains text.

INVALIDATES:

• Dutch Guidelines: validateRpd7s4()
  • https://github.com/xwiki/xwiki-platform/blob/master/xwiki-platform-tools/xwiki-platform-tool-standards-validator/src/main/java/org/xwiki/validator/DutchWebGuidelinesValidator.java#L716-L739
• R-pd.7.4 "Images placed in a link should have a non-empty text alternative to enable visitors who do not see the image to follow the link."

EXPLANATION:

• We have 3 links with images (img) in an empty page. 2 of these 3 links fail the validation.
  • Fail - Ex1:

    <a href="/xwiki/bin/view/Main/" title="Home" rel="home" class="navbar-brand">
      <img src="/xwiki/bin/download/FlamingoThemes/Iceberg/logo.svg" alt="Wiki Logo"/>
    </a>
    

  • Fail - Ex2:

    <a href="/xwiki/bin/view/XWiki/Admin">
      <img class='avatar avatar_120' src='/xwiki/bin/skin/resources/icons/xwiki/noavatar.png' alt='Administrator' title='Administrator'/>
    </a>
    

  • Success - Ex3:

    <a href="/xwiki/bin/view/XWiki/Admin" class="icon-navbar">
      <span class="sr-only">User Profile</span>
      <img class='avatar avatar_50' src='/xwiki/bin/skin/resources/icons/xwiki/noavatar.png' alt='Administrator' title='Administrator'/>
    </a>

• The alt values for all these images are non-empty, so the test should validate.

FIXES:

• VAR1: Fix the test validation so that the non-empty alt attributes are detected
• VAR2: Add text inside the link node using the .sr-only class