minor fix can not delete if record have move

exceptions.py

@@ -12,6 +12,9 @@ class ImportDataEmployeeError(ValidationError):
 class LiquidationEmployeeError(UserError):
     pass
 
+class LiquidationDeleteError(UserError):
+    pass
+
 
 class LiquidationMoveError(UserError):
     pass

liquidation.py

@@ -10,7 +10,7 @@ from trytond.transaction import Transaction
 from trytond.i18n import gettext
 from .exceptions import (
     LiquidationEmployeeError, MissingSecuenceLiquidation,
-    LiquidationMoveError, WageTypeConceptError
+    LiquidationMoveError, WageTypeConceptError, LiquidationDeleteError
 )
 
 STATES = {'readonly': (Eval('state') != 'draft')}
@@ -456,6 +456,19 @@ class Liquidation(Workflow, ModelSQL, ModelView):
         ])
         return lines
 
+    @classmethod
+    def delete(cls, records):
+        # Cancel before delete
+        cls.cancel(records)
+        for liquidation in records:
+            if liquidation.state != 'cancel':
+                raise LiquidationDeleteError(
+                    gettext('staff_payroll_co.msg_delete_cancel', liquidation=liquidation.rec_name))
+            if liquidation.move:
+                raise LiquidationDeleteError(
+                    gettext('staff_payroll_co.msg_existing_move', liquidation=liquidation.rec_name))
+        super(Payroll, cls).delete(records)
+
     def set_liquidation_lines(self):
         pool = Pool()
         Payroll = pool.get('staff.payroll')

message.xml

@@ -58,5 +58,12 @@ this repository contains the full copyright notices and license terms. -->
         <record model="ir.message" id="msg_missing_party">
             <field name="text">Missing party in mandatory wage "%(wage)s" for employee "%(employee)s"</field>
         </record>
+
+        <record model="ir.message" id="msg_delete_cancel">
+            <field name="text">Liquidation "%(liquidation)s" must be cancelled before deletion.</field>
+        </record>
+        <record model="ir.message" id="msg_existing_move">
+            <field name="text">Liquidation "%(liquidation)s" has a move, must be deleted before deletion.</field>
+        </record>
     </data>
 </tryton>