The spacewalk-repo-sync command fails with error 'yum.Errors.RepoError: Cannot retrieve repository metadata (repomd.xml) for repository' after adding http proxy entries to /etc/rhn/rhn.conf

Issue

• The spacewalk-repo-sync command fails with following error after adding http proxy entries to /etc/rhn/rhn.conf

[root@]# spacewalk-repo-sync --channel epel-5-x86_64 --type yum
Traceback (most recent call last):
  File "/usr/bin/spacewalk-repo-sync", line 72, in ?
    sys.exit(abs(main() or 0))
  File "/usr/bin/spacewalk-repo-sync", line 66, in main
    sync.main()
  File "/usr/share/rhn/satellite_tools/reposync.py", line 103, in main
    self.import_packages(plugin, url)
  File "/usr/share/rhn/satellite_tools/reposync.py", line 135, in import_packages
    packages = plug.list_packages()
  File "/usr/share/rhn/satellite_tools/repo_plugins/yum_src.py", line 75, in list_packages
    sack.populate(repo, 'metadata', None, 0)
  File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 168, in populate
    if self._check_db_version(repo, mydbtype):
  File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 226, in _check_db_version
    return repo._check_db_version(mdtype)
  File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1226, in _check_db_version
    repoXML = self.repoXML
  File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1399, in <lambda>
    repoXML = property(fget=lambda self: self._getRepoXML(),
  File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1395, in _getRepoXML
    raise Errors.RepoError, msg
yum.Errors.RepoError: Cannot retrieve repository metadata (repomd.xml) for repository: epel-5-x86_64. Please verify its path and try again

• Another example of the problem:

# spacewalk-repo-sync --channel puppetlabs-products --url=http://yum.puppetlabs.com/el/6.4/products/x86_64/
Repo URL: http://yum.puppetlabs.com/el/6.4/products/x86_64/
ERROR: Cannot retrieve repository metadata (repomd.xml) for repository: puppetlabs-products. Please verify its path and try again
Sync completed.
Total time: 0:00:00