Refactor ConsoleLog (#7428)

CONTRIBUTING.md

@@ -326,6 +326,31 @@ cd superset
 FLASK_ENV=development flask run -p 8088 --with-threads --reload --debugger
 ```
 
+#### Logging to the browser console
+
+This feature is only available on Python 3. When debugging your application, you can have the server logs sent directly to the browser console using the [ConsoleLog](https://github.com/betodealmeida/consolelog) package. You need to mutate the app, by adding the following to your `config.py` or `superset_config.py`:
+
+```python
+from console_log import ConsoleLog
+
+def FLASK_APP_MUTATOR(app):
+    app.wsgi_app = ConsoleLog(app.wsgi_app, app.logger)
+```
+
+Then make sure you run your WSGI server using the right worker type:
+
+```bash
+FLASK_ENV=development gunicorn superset:app -k "geventwebsocket.gunicorn.workers.GeventWebSocketWorker" -b 127.0.0.1:8088 --reload
+```
+
+You can log anything to the browser console, including objects:
+
+```python
+from superset import app
+app.logger.error('An exception occurred!')
+app.logger.info(form_data)
+```
+
 ### Frontend Assets
 
 Frontend assets (JavaScript, CSS, and images) must be compiled in order to properly display the web UI. The `superset/assets` directory contains all NPM-managed front end assets. Note that there are additional frontend assets bundled with Flask-Appbuilder (e.g. jQuery and bootstrap); these are not managed by NPM, and may be phased out in the future.