Made use of app.errorhandler

app/__init__.py

 # third-party imports
-from flask import Flask
+from flask import Flask, render_template
 from flask_sqlalchemy import SQLAlchemy
 from flask_login import LoginManager
 from flask_migrate import Migrate
@@ -35,4 +35,17 @@ def create_app(config_name):
     from .home import home as home_blueprint
     app.register_blueprint(home_blueprint)
 
+    @app.errorhandler(403)
+    def forbidden(error):
+        return render_template('errors/403.html', title='Forbidden'), 403
+
+    @app.errorhandler(404)
+    def page_not_found(error):
+        return render_template('errors/404.html', title='Page Not Found'), 404
+
+    @app.errorhandler(500)
+    def internal_server_error(error):
+        return render_template('errors/500.html', title='Server Error'), 500
+
+
     return app