add proper error pages for 404, 500

assets/styles.css

@@ -257,3 +257,10 @@ form.btn-group {
 .clearfix {
     clear: both;
 }
+
+section > pre.error-log {
+    overflow: auto;
+    padding-top: 2em;
+    padding-bottom: 2em;
+    opacity: 0.7;
+}

routes.py

@@ -54,6 +54,17 @@ def touch_viewer(resp):
     return resp
 
 
+@app.errorhandler(404)
+def not_found(e):
+    return (render_template('404.html', e=e), 404)
+
+
+@app.errorhandler(500)
+@app.errorhandler(Exception)
+def internal_server_error(e):
+    return (render_template('500.html', e=e), 500)
+
+
 @app.route('/')
 def index():
     if g.viewer:

templates/404.html

@@ -0,0 +1,12 @@
+{% extends 'lib/layout.html' %}
+
+{% block body -%}
+<section>
+    <h2>Nothing here</h2>
+    <p>It seems you may have gotten lost. <a href='/'>Head back</a></p>
+    <pre class='error-log'>
+    404 Not Found
+
+    {{e}}</pre>
+</section>
+{% endblock %}

templates/500.html

@@ -0,0 +1,24 @@
+{% extends 'lib/layout.html' %}
+
+{% block body -%}
+
+<section>
+    <h2>Something unexpected happened!</h2>
+    <p>
+    {%- if g.sentry_event_id %}
+    This error has been logged, please try again in a few minutes.
+    {%- else %}
+    Please try again in a few minutes.
+    {%- endif %}
+    </p>
+    <pre class='error-log'>
+    500 Internal server error
+
+    {{e}}
+
+    {%- if g.sentry_event_id %}
+    sentry://{{ g.sentry_event_id }}
+    {%- endif %}</pre>
+</section>
+
+{%- endblock %}