turn off escaping for aria-describedby attribute

common/lib/capa/capa/templates/formulaequationinput.html

@@ -5,7 +5,7 @@
   <div class="${status.classname}" id="status_${id}">
     <input type="text" name="input_${id}" id="input_${id}"
         data-input-id="${id}" value="${value}"
-        ${describedby}
+        ${describedby| n}
         % if size:
         size="${size}"
         % endif

common/lib/capa/capa/templates/textline.html

@@ -20,7 +20,7 @@
 % for description_id, description_text in response_data['descriptions'].items():
     <p class="question-description" id="${description_id}">${description_text}</p>
 % endfor
-<input type="text" name="input_${id}" id="input_${id}" ${describedby} value="${value}"
+<input type="text" name="input_${id}" id="input_${id}" ${describedby| n} value="${value}"
     % if do_math:
         class="math"
     % endif