While updating the source code of a process definition through Guvnor Rest API the standalone code complaints with 415 unsupported Media Type

Issue

• While updating the source code of a process definition through the following Guvnor (i.e. BRM) Rest API [1][2] the standalone code complaints with 415 unsupported Media Type exception. The content-type for the PUT method while doing the Rest API call was set to plain/text with similar data as shown below.

<?xml version="1.0" encoding="UTF-8"?>
<bpmn2:definitions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.omg.org/bpmn20" xmlns:bpmn2="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" xmlns:drools="http://www.jboss.org/drools" id="_biVLYHgOEeOukJMI5uok0A" xsi:schemaLocation="http://www.omg.org/spec/BPMN/20100524/MODEL BPMN20.xsd" targetNamespace="http://www.omg.org/bpmn20">
  <bpmn2:process id="Sample.ProcessTesting" drools:packageName="org.jboss.process.test" name="ProcessTesting" isExecutable="true">
    <bpmn2:startEvent id="_41B1EF91-B0BF-4A3A-96A9-A03BF18C41C8" drools:bgcolor="#9acd32" drools:selectable="true" name="StartNode">
      <bpmn2:outgoing>_5E97A41F-B299-40E9-B342-C790981AD5E6</bpmn2:outgoing>
    </bpmn2:startEvent>
    ...
  </bpmndi:BPMNDiagram>
</bpmn2:definitions>

How to fix this issue?

[1] http://localhost:8080/jboss-brms/rest/packages/{packageName}/assets/{assetName}/source
[2] Accessing Rules by Package