Update error handling to work with werkzeug 2

Closes: #1

templates/show_error.html

@@ -7,24 +7,17 @@
 {% block content %}
 <div class="p-2">
 
-<h1>Software error: {{ tb.exception_type }}</h1>
+<h1>Software error: {{ exception_type }}</h1>
 <div>
-  <pre>{{ tb.exception }}</pre>
+  <pre>{{ exception }}</pre>
 </div>
 
-{% set body %}
-URL: {{ request.url }}
-
-{{ tb.plaintext | safe }}
-{% endset %}
-
-<p><a class="btn btn-primary btn-lg" role="button" href="https://github.com/EdwardBetts/dab-mechanic/issues/new?title={{ tb.exception + " " + request.url | urlencode }}&body={{ body | urlencode }}">Submit as an issue on GitHub</a> (requires an account with GitHub)</p>
-
 <h2 class="traceback">Traceback <em>(most recent call last)</em></h2>
-{{ tb.render_summary(include_title=False) | safe }}
+{{ summary | safe }}
+
+<p>Error in function "{{ last_frame.f_code.co_name }}": {{ last_frame_args | pprint }}</p>
+<pre>{{ last_frame.f_locals | pprint }}</pre>
 
-<p>Error in function "{{ last_frame.function_name }}": {{ last_frame_args | pprint }}</p>
-<pre>{{ last_frame.locals | pprint }}</pre>
 </div>
 
 {% endblock %}