[Satellite 6] Unable to register RHEL7 host to Satellite "[ERROR] BadStatusLine: ' '"

Issue

• Unable to register a host to Red Hat Satellite 6 Server. subscription-manager fails with error BadStatusLine.
  Below error is seen in /var/log/rhsm/rhsm.log:

Traceback (most recent call last):
  File "/usr/lib64/python2.7/site-packages/subscription_manager/managercli.py", line 1113, in _do_command
    type=self.options.consumertype
  File "/usr/lib64/python2.7/site-packages/rhsmlib/services/register.py", line 80, in register
    type=type
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 966, in registerConsumer
    return self.conn.request_post(url, params)
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 693, in request_post
    return self._request("POST", method, params, headers=headers)
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 716, in _request
    info=info, headers=headers)
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 573, in _request
    response = conn.getresponse()
  File "/usr/lib64/python2.7/httplib.py", line 1113, in getresponse
    response.begin()
  File "/usr/lib64/python2.7/httplib.py", line 444, in begin
    version, status, reason = self._read_status()
  File "/usr/lib64/python2.7/httplib.py", line 408, in _read_status
    raise BadStatusLine(line)
BadStatusLine: ''