Adding error 404 catcher

aurweb/routers/errors.py

+from aurweb.templates import make_context, render_template
+from aurweb import l10n
+
+
+async def not_found(request, exc):
+    _ = l10n.get_translator_for_request(request)
+    context = make_context(request, f"404 - {_('Page Not Found')}")
+    return render_template("errors/404.html", context)
+
+
+# Maps HTTP errors to functions
+exceptions = {
+    404: not_found,
+}

templates/errors/404.html

+{% extends 'partials/layout.html' %}
+
+{% block pageContent %}
+  <div class="box 404">
+    <h2>404 - {% trans %}Page Not Found{% endtrans %}</h2>
+    <p>{% trans %}Sorry, the page you've requested does not exist.{% endtrans %}</p>
+  </div>
+  {% endblock %}