Revert "Remove showing errors from build.error"

This reverts commit d4951a8.

We decided to keep this code around for now.
See #10980 (comment)

Author: humitos

readthedocs/templates/builds/build_detail.html

@@ -225,6 +225,31 @@ <h3>{{ notification.get_message.type|title }}</h3>
     {% endif %}
     {% endfor %}
 
+      <div class="build-error"
+           data-bind="visible: error"
+           style="display: none;">
+        <h3>{% trans "Error" %}</h3>
+        <p class="build-error"
+           data-bind="text: error">
+            {#
+              I'd like to use ``build.error|urlize`` here, so we can have nice links.
+              However, this is not possible because we are using `data-bind="text: error"`
+              which means that Knockout.js will use the `.error` attribute to fill
+              the content of this tag dynamically.
+            #}
+            {{ build.error|urlize }}
+        </p>
+        <p>
+          {% block github_issue_link %}
+            {% if issue_url %}
+              {% blocktrans trimmed with url=issue_url %}
+                <a href="{{ url }}">Report any build issues here</a>.
+              {% endblocktrans %}
+            {% endif %}
+          {% endblock %}
+        </p>
+      </div>
+
       <div id="build-commands"
            class="build-command-list"
            data-bind="visible: commands, foreach: display_commands"