When you have an incompatible license and you start Confluence you get a Johnson error telling you to enter a new license via fixonly/fixlicense.action.

If you then enter another incompatible license, instead of a proper error message you get -

$soyTemplateRendererHelper.getRenderedTemplateHtml("com.atlassian.auiplugin:aui-experimental-soy-templates", "aui.message.error.soy", {"content" : $error, "id" : "${fieldname}-error"})

See the screenshot.