add missing error_message workflow variable

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@8199 20353a03-c40f-0410-a6d1-a30d3c3de9de

bt5/erp5_forge/WorkflowTemplateItem/portal_workflow/bug_workflow/variables/error_message.xml

+<?xml version="1.0"?>
+<ZopeData>
+  <record id="1" aka="AAAAAAAAAAE=">
+    <pickle>
+      <tuple>
+        <tuple>
+          <string>Products.DCWorkflow.Variables</string>
+          <string>VariableDefinition</string>
+        </tuple>
+        <none/>
+      </tuple>
+    </pickle>
+    <pickle>
+      <dictionary>
+        <item>
+            <key> <string>__ac_local_roles__</string> </key>
+            <value>
+              <none/>
+            </value>
+        </item>
+        <item>
+            <key> <string>_owner</string> </key>
+            <value>
+              <none/>
+            </value>
+        </item>
+        <item>
+            <key> <string>id</string> </key>
+            <value> <string>error_message</string> </value>
+        </item>
+      </dictionary>
+    </pickle>
+  </record>
+</ZopeData>