Uploading content certificates to Red Hat Update Infrastructure 2.1 fails with "TypeError: argument of type 'NoneType' is not iterable"

Issue

• Uploading content certificates to a RHUA 2.1 instance fails with an error similar to:

  An unexpected error has occurred during the last operation.
  More information can be found in /root/.rhui/rhui.log.
  

  Error in /root/.rhui/rhui.log:

  Connecting to RHUA [RHUA.EXAMPLE.COM]...
  Successfully connected to [RHUA.EXAMPLE.COM]
  Unexpected error caught at the shell level
  Traceback (most recent call last):
    File "/usr/lib/python2.6/site-packages/rhui/tools/shell.py", line 86, in safe_listen
      self.listen(clear=first_run)
    File "/usr/lib/python2.6/site-packages/rhui/tools/shell.py", line 112, in listen
      Shell.listen(self)
    File "/usr/lib/python2.6/site-packages/rhui/common/shell.py", line 186, in listen
      item.func(*args, **item.kwargs)
    File "/usr/lib/python2.6/site-packages/rhui/tools/screens/entitlements.py", line 104, in new_certificate
      self.cert_manager.add_certificate(cert_filename)
    File "/usr/lib/python2.6/site-packages/rhui/tools/cert_manager.py", line 276, in add_certificate
      if not _is_valid_download_url(e.download_url):
    File "/usr/lib/python2.6/site-packages/rhui/tools/cert_manager.py", line 301, in _is_valid_download_url
      if valid_url in download_url:
  TypeError: argument of type 'NoneType' is not iterable