erp5_base: check consistency when start assignment

   Prevent the user start an inconsistent assignment, since, extra property sheets can include some
   business logic around assignment configuration.

bt5/erp5_base/WorkflowTemplateItem/portal_workflow/assignment_workflow/script_Assignment_checkConsistency.py

+assignment = state_change['object']
+assignment.Base_checkConsistency()

bt5/erp5_base/WorkflowTemplateItem/portal_workflow/assignment_workflow/script_Assignment_checkConsistency.xml

+<?xml version="1.0"?>
+<ZopeData>
+  <record id="1" aka="AAAAAAAAAAE=">
+    <pickle>
+      <global name="Workflow Script" module="erp5.portal_type"/>
+    </pickle>
+    <pickle>
+      <dictionary>
+        <item>
+            <key> <string>_bind_names</string> </key>
+            <value>
+              <object>
+                <klass>
+                  <global name="_reconstructor" module="copy_reg"/>
+                </klass>
+                <tuple>
+                  <global name="NameAssignments" module="Shared.DC.Scripts.Bindings"/>
+                  <global name="object" module="__builtin__"/>
+                  <none/>
+                </tuple>
+                <state>
+                  <dictionary>
+                    <item>
+                        <key> <string>_asgns</string> </key>
+                        <value>
+                          <dictionary>
+                            <item>
+                                <key> <string>name_container</string> </key>
+                                <value> <string>container</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_context</string> </key>
+                                <value> <string>context</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_m_self</string> </key>
+                                <value> <string>script</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_subpath</string> </key>
+                                <value> <string>traverse_subpath</string> </value>
+                            </item>
+                          </dictionary>
+                        </value>
+                    </item>
+                  </dictionary>
+                </state>
+              </object>
+            </value>
+        </item>
+        <item>
+            <key> <string>_params</string> </key>
+            <value> <string>state_change</string> </value>
+        </item>
+        <item>
+            <key> <string>_proxy_roles</string> </key>
+            <value>
+              <tuple>
+                <string>Manager</string>
+              </tuple>
+            </value>
+        </item>
+        <item>
+            <key> <string>description</string> </key>
+            <value>
+              <none/>
+            </value>
+        </item>
+        <item>
+            <key> <string>id</string> </key>
+            <value> <string>script_Assignment_checkConsistency</string> </value>
+        </item>
+        <item>
+            <key> <string>portal_type</string> </key>
+            <value> <string>Workflow Script</string> </value>
+        </item>
+        <item>
+            <key> <string>title</string> </key>
+            <value>
+              <none/>
+            </value>
+        </item>
+      </dictionary>
+    </pickle>
+  </record>
+</ZopeData>

bt5/erp5_base/WorkflowTemplateItem/portal_workflow/assignment_workflow/transition_open_action.xml

@@ -20,6 +20,7 @@
               <tuple>
                 <string>action_type/workflow</string>
                 <string>after_script/portal_workflow/assignment_workflow/transition_open</string>
+                <string>before_script/portal_workflow/assignment_workflow/script_Assignment_checkConsistency</string>
               </tuple>
             </value>
         </item>