strange behaviour of colon within string

[khany]

hello all,

i am relatively new to python and i am trying to convert a php app i
have over to it using googleapps.

anyway here is the problem. i poll ebay API which has in its XML "<?
xml version="1.0" encoding="utf-8"?><findItemsAdvancedRequest
xmlns="http://www.ebay.com/marketplace/search/v1/services">  .... "

however it fails to create the string UNLESS i remove the colon (:) in
the http section. i tried to substitute it with chr(58) but it errors
the same without showing why. does anyone know what i am doing wrong?
is this peculiar to googleapps?

thanks