Add the Product.complete_size convenience attribute

also define `str(VendorItem)`

corepos/db/office_op/model.py

@@ -611,6 +611,18 @@ class Product(Base):
         fields = filter(bool, fields)
         return ' '.join(fields)
 
+    @property
+    def complete_size(self):
+        """
+        Returns the "complete" size string for the product.  This is based on
+        the :attr:`size` and :attr:`unit_of_measure` attributes.
+        """
+        parts = [self.size, self.unit_of_measure]
+        parts = [(part or '').strip()
+                 for part in parts]
+        parts = [part for part in parts if part]
+        return " ".join(parts).strip()
+
     def __str__(self):
         return self.description or ''
 
@@ -771,6 +783,9 @@ class VendorItem(Base):
 
     modified = sa.Column(sa.DateTime(), nullable=True)
 
+    def __str__(self):
+        return "{} from {}".format(self.sku, self.vendor)
+
 
 class ScaleItem(Base):
     """