check for valid address data

mixin.py

@@ -8,6 +8,7 @@ from decimal import Decimal
 import html
 from trytond.exceptions import UserError
 from trytond.i18n import gettext
+from trytond.tools import cached_property
 
 
 class EdocumentMixin(object):
@@ -15,6 +16,52 @@ class EdocumentMixin(object):
     """
     __slots__ = ()
 
+    @cached_property
+    def seller_trade_address(self):
+        """ get address of seller, throw exception if incomplete
+
+        Raises:
+            UserError: if no address
+            UserError: if no country on address
+
+        Returns:
+            record : model party.address
+        """
+        result = super(EdocumentMixin, self).seller_trade_address
+        if not result:
+            raise UserError(gettext(
+                'edocument_xrechnung.msg_no_seller_address',
+                sellerparty=self.invoice.company.rec_name
+                if self.invoice and self.invoice.company
+                else '-'))
+        if not result.country:
+            raise UserError(gettext(
+                'edocument_xrechnung.msg_no_address_country',
+                party=result.party))
+        return result
+
+    @cached_property
+    def buyer_trade_address(self):
+        """ exception if no address
+
+        Returns:
+            record: model party.address
+        """
+        if (self.invoice.type == 'out') and (
+                not self.invoice.invoice_address):
+            raise UserError(gettext(
+                'edocument_xrechnung.msg_no_buyer_address',
+                buyerparty=self.invoice.party.rec_name
+                if self.invoice and self.invoice.party
+                else '-'))
+
+        result = super(EdocumentMixin, self).buyer_trade_address
+        if result and not result.country:
+            raise UserError(gettext(
+                'edocument_xrechnung.msg_no_address_country',
+                party=result.party))
+        return result
+
     def get_list_of_comments(self):
         """ comment, to export in <ram:IncludedNote/>