add email_str property to get "encoded" version of email address

themis/datatypes/address.py

@@ -54,6 +54,12 @@ class Address(Field):
         return o
     from_dict = classmethod(from_dict)
 
+    @property
+    def email_str(self):
+        if not self.email:
+            return ''
+        return self.email.replace('@', ' arobase ').replace('.', ' point ')
+
 class IAddressWidget(IWidget):
     pass