Fix not imported os and format code

example-flask-python3.6-index/app/main.py

@@ -1,15 +1,20 @@
+import os
+
 from flask import Flask, send_file
 app = Flask(__name__)
 
+
 @app.route("/hello")
 def hello():
     return "Hello World from Flask in a uWSGI Nginx Docker container with \
      Python 3.6 (from the example template)"
 
+
 @app.route("/")
 def main():
     return send_file('./static/index.html')
 
+
 # Everything not declared before (not a Flask route / API endpoint)...
 @app.route('/<path:path>')
 def route_frontend(path):
@@ -22,5 +27,6 @@ def route_frontend(path):
     else:
         return send_file('./static/index.html')
 
+
 if __name__ == "__main__":
     app.run(host='0.0.0.0', debug=True, port=80)