Page redirects are not working in my flask app

In some versions of Domino users may notice issues with flask app redirects. This can show up when users are being sent to a secondary page of the app or when clicking a link in the app is supposed to download a file. 

If you are using a chrome browser and use developer tools (View > Developer > Developer Tools), you may see the following errors when attempting the flask redirects in your app: 

Network details for the error: 
Request URL: <app url> 
Request Method: GET
Status Code: 302 
Referrer Policy: strict-origin-when-cross-origin

 or 

Mixed Content: The page at '<app url> was loaded over HTTPS, but requested an 
insecure resource 'http://<run_id>-domino-compute.svc.cluster.local/<userid>/
<project_name>/r/notebookSession/<runid>/<redirect_page>'. This request has been 
blocked; the content must be served over HTTPS.

To remediate this issue we'll want to slightly adjust the ReverseProxied function, which we've taken from the Domino docs (found here): 

class ReverseProxied(object):
  def __init__(self, app):
      self.app = app
  def __call__(self, environ, start_response):
      script_name = environ.get('HTTP_X_SCRIPT_NAME', '')
      if script_name:
          environ['SCRIPT_NAME'] = script_name
          path_info = environ['PATH_INFO']
          if path_info.startswith(script_name):
              environ['PATH_INFO'] = path_info[len(script_name):]
      #flask fix              
      # Setting wsgi.url_scheme from Headers set by proxy before app
      scheme = environ.get('HTTP_X_SCHEME', 'https')
      if scheme:
        environ['wsgi.url_scheme'] = scheme
        # Setting HTTP_HOST from Headers set by proxy before app
      remote_host = environ.get('HTTP_X_FORWARDED_HOST', '')
      remote_port = environ.get('HTTP_X_FORWARDED_PORT', '')
      if remote_host and remote_port:
          environ['HTTP_HOST'] = f'{remote_host}:{remote_port}'
      #end flaskfix 
      return self.app(environ, start_response)

As you can see, the only change was to add the lines between #flaskfix and #end flaskfix, posted below: 

      #flask fix              
      # Setting wsgi.url_scheme from Headers set by proxy before app
      scheme = environ.get('HTTP_X_SCHEME', 'https')
      if scheme:
        environ['wsgi.url_scheme'] = scheme
        # Setting HTTP_HOST from Headers set by proxy before app
      remote_host = environ.get('HTTP_X_FORWARDED_HOST', '')
      remote_port = environ.get('HTTP_X_FORWARDED_PORT', '')
      if remote_host and remote_port:
          environ['HTTP_HOST'] = f'{remote_host}:{remote_port}'
      #end flask fix