Error loading the WSDL in Browser : User Not Authorized

1. When opening a WDSL URL, for example: https://<instance-name>.service-now.com/incident.do?WSDL
   You will see the Message:  User Not Authorized
   
   
   
2. When loading the WSDL in the SOAP UI. You will see the message Error loading WSDL.
   The full error message is:
   Error loading [the WSDL URL]: org.apache.xmlbeans.SmlExcpetion: org.apache.xmlbeans.XmlException: error: Unexpected element: CDATA
   
   

This issue can be observed when the Basic Authentication has been turned off for WSDL Web Services. Out of the Box, all the WSDL request requires authentication when a user tries to open the WSDL (when the user is not already logged in the instance). See the screenshot below:

Set the system property glide.basicauth.required.wsdl to true.

You will see the following message in the logs when reproducing the issue:

2018-04-26 14:02:20 (513) Default-thread-11 4D877810137993007A22DD828144B0F9 *** End #20914 /api/now/ui/date_time/legacy, user: guest, total time: 0:00:00.010, processing time: 0:00:00.010, SQL time: 0:00:00.001 (count: 2) , type:rest, method:GET, api_name:now/ui, resource:now/ui/date_time/legacy, version:Default, user_id:5136503cc611227c0183e96598c4f706, response_status:200
2018-04-26 14:10:35 (263) http-20 New transaction 4D877810137993007A22DD828144B0F9 #20938 /incident.do
2018-04-26 14:10:35 (270) API_INT-thread-3 4D877810137993007A22DD828144B0F9 Security restrictions on WSDLProcessor
2018-04-26 14:10:35 (271) API_INT-thread-3 4D877810137993007A22DD828144B0F9 *** End #20938 /incident.do, user: guest, total time: 0:00:00.000, processing time: 0:00:00.000, SQL time: 0:00:00.000 (count: 3)