Add check that invoices do not exist already before import.

account.py

@@ -107,6 +107,19 @@ def convert_account(account):
     else:
         return account
 
+def find_factura(number, company):
+    pool = Pool()
+    Invoice = pool.get('account.invoice')
+    invoice, = Invoice.search([('number', '=', number),
+                               ('company', '=', company)], limit=1)
+    return invoice
+    
+def check_factura_not_exists(number, company):
+    if find_factura(number, company):
+        raise UserError(
+            gettext('account_import_contaplus.msg_factura_exists',
+                    number=number))
+
 
 class Move(metaclass=PoolMeta):
     __name__ = 'account.move'
@@ -339,6 +352,7 @@ class AccountImportContaplus(Wizard):
             invoice.sii_issued_key = '02'
         return invoice
 
+        
 
     def import_invoices(self, company, imp_record):
         pool = Pool()
@@ -367,6 +381,8 @@ class AccountImportContaplus(Wizard):
             invoice_number = iline.serie + iline.factura
             if invoice_number not in to_create:
                 # todo check num factura not alredy there.
+                check_factura_not_exists(invoice_number, company)
+                
                 if invoice:
                     # check factura
                     # if lines empty remove from to_create

message.xml

@@ -24,5 +24,8 @@
     <record model="ir.message" id="msg_missing_payment_term">
       <field name="text">Payment terms missing for %(party)s.</field>
     </record>
-  </data>
+    <record model="ir.message" id="msg_factura_exists">
+      <field name="text">Invoice "%(number)s" already exists for this company.</field>
+    </record>
+ </data>
 </tryton>