python code snippet using requests

I need a small python code snippet which does the following : Using requests library define a function which : 1) Loop through a txt file of http (and https) proxies proxies in the format user:pass@ip:port 2) Using requests library, create a get request to a url (can be http or https) via proxy 3) Catch any ProxyError (can be authentication or network error) move to next proxy 4) Catch 502, 503, 504 errors and retry 3 times (perhaps use [login to view URL]) 5) Return either the raw requests response or the Error