Commented explanation of PORT_ENV_VAR_KEY.

app.py

@@ -6,10 +6,10 @@ from flask import Flask, send_from_directory, request, redirect
 from flask_cors import CORS
 from flask_compress import Compress
 
-import config
 from database.db import lookup_db_for_binding, init_all_dbs_with_app, init_binding_to_db_for_bindings
-from config.config import APP_NAME, ENV, DEBUG_MODE, get_app_config, get_static_url
+from config.config import DEBUG_MODE, get_app_config, get_static_url
 
+# The environment variable whose value is the PORT this application will listen on
 PORT_ENV_VAR_KEY = "PORT"
 
 # Create and configure our Flask app