Using heroku with python results in http:500 error

Question

I have a python app which pulls xml data through http. I want to run this app on Heroku. The app runs fine on Heroku if I just return "hello world" without trying to pull the xml. When I run this app locally (either by using the 'foreman' command, or just through python directly) it runs completely fine, and the "response.status" is 200, as expected. If I deploy to Heroku, it runs fine up to that point, but I get a response.status: 500 instead, and so cannot retrieve the XML data.

What might be causing this problem?

Here is the relevant function.

Edit: I have tried other URLs with the same results: I get an HTTP status 200 when run locally, but 500 when run on Heroku

def fetchBoBXml():
  # Fetch XML info from BoB
  conn = httplib.HTTPConnection(BOB_DOMAIN, BOB_PORT)
  conn.request("GET", BOB_URL)
  response = conn.getresponse()
  status = response.status
  if status != 200:
    print "BOB response status %s" % status
    raise Exception("BoB HTTP response status: %s" % status)
  data = response.read()
  conn.close()  
  return data