subscription-manager fails with Error during registration URL can't contain control characters.

Issue

• System registration to customer portal fails with the below error:

  2025-09-08 10:08:46,838 [ERROR] subscription-manager:149576:MainThread @managercli.py:230 - Error during registration: URL can't contain control characters. '/subscription\nport = 443/users/<Username>/owners' (found at least '\n')
  2025-09-08 10:08:46,839 [ERROR] subscription-manager:149576:MainThread @managercli.py:231 - URL can't contain control characters. '/subscription\nport = 443/users/<Username>/owners' (found at least '\n')
  Traceback (most recent call last):
    File "/usr/lib64/python3.6/site-packages/subscription_manager/managercli.py", line 2029, in _do_command
      no_owner_cb=self._no_owner_cb
    File "/usr/lib64/python3.6/site-packages/rhsmlib/services/register.py", line 202, in determine_owner_key
      owners = self.cp.getOwnerList(username)
    File "/usr/lib64/python3.6/site-packages/rhsm/connection.py", line 1493, in getOwnerList
      owners = self.conn.request_get(method)
    File "/usr/lib64/python3.6/site-packages/rhsm/connection.py", line 1013, in request_get
      return self._request("GET", method, headers=headers, cert_key_pairs=cert_key_pairs)
    File "/usr/lib64/python3.6/site-packages/rhsm/connection.py", line 1046, in _request
      info=info, headers=headers, cert_key_pairs=cert_key_pairs)
    File "/usr/lib64/python3.6/site-packages/rhsm/connection.py", line 822, in _request
      conn.request(request_type, handler, body=body, headers=final_headers)
    File "/usr/lib64/python3.6/http/client.py", line 1273, in request
      self._send_request(method, url, body, headers, encode_chunked)
    File "/usr/lib64/python3.6/http/client.py", line 1284, in _send_request
      self.putrequest(method, url, **skips)
    File "/usr/lib64/python3.6/http/client.py", line 1137, in putrequest
      raise InvalidURL(f"URL can't contain control characters. {url!r} "
  http.client.InvalidURL: URL can't contain control characters. '/subscription\nport = 443/users/<Username>/owners' (found at least '\n')