Message 235666 - Python tracker

In the initial report, I thought, it was mentioned that curl reads the same http_proxy variable properly.  It will be good to have a correct curl test case to ascertain that. 

But, at all the places, where @ character is allowed in urls (netrc, git configs, I see that @ should be encoded). In that case, this bug report is more towards detecting bad urls and presenting a better error message.