Fix syntax issue

Author: vadave

{{cookiecutter.app_slug}}/project/server/__init__.py

@@ -77,7 +77,7 @@ def server_error_page(error):
 
     # shell context for flask cli
     @app.shell_context_processor
-    def ctx()
+    def ctx():
         return {'app': app, 'db': db}
 
     return app