Create 404 catch-all page

create_app.py

@@ -1,4 +1,4 @@
-from flask import Flask
+from flask import Flask, render_template
 from flask_sqlalchemy import SQLAlchemy
 from flask_login import LoginManager
 
@@ -31,6 +31,11 @@ def create_app():
     from .routes import blueprint as routes_blueprint
     app.register_blueprint(routes_blueprint)
 
+    @app.errorhandler(404)
+    def page_not_found(e):
+        # note that we set the 404 status explicitly
+        return render_template('errors/404.html'), 404
+
     # CLI commands setup
     @app.shell_context_processor
     def shell_context():

templates/errors/404.html

@@ -0,0 +1,19 @@
+{% extends 'layouts/index.html' %}
+
+{% block content %}
+    <div class="content-inner" style="display: flex">
+        <div style="margin: 0 auto;">
+            <h2>404 - Content Not Found</h2>
+            <p>
+                {% if current_user.is_authenticated %}
+                    Sorry <strong>{{ current_user.username }}</strong>, the
+                {% else %}
+                    The
+                {% endif %} content you requested could not be found.
+                <br>
+                It may have been deleted or moved somewhere else.
+                <span style="text-align: center">Go <a href="{{ url_for('main.index') }}">home?</a></span>
+            </p>
+        </div>
+    </div>
+{% endblock %}