Description of problem:
With repositories configured with proxy=_none_ Yum works as expected if ftp/http/https_proxy is not set. However, with http_proxy set Yum tries to use the proxy for such repositories. This will cause Yum to fail to contact repositories which cannot be accessed thru a proxy.

As per IRC discussion, this seems to be caused by Yum not instructing libcurl to ignore the environment variables.

Version-Release number of selected component (if applicable):
Fedora 17 Beta