After verification fill in class members

bitshares/message.py

@@ -49,6 +49,8 @@ class Message(BlockchainInstance):
     def __init__(self, message, *args, **kwargs):
         BlockchainInstance.__init__(self, *args, **kwargs)
         self.message = message
+        self.signed_by_account = None
+        self.signed_by_name = None
 
     def sign(self, account=None, **kwargs):
         """ Sign a message with an account's memo key
@@ -91,6 +93,9 @@ def sign(self, account=None, **kwargs):
             wif
         )).decode("ascii")
 
+        self.signed_by_account = account
+        self.signed_by_name = account["name"]
+
         return SIGNED_MESSAGE_ENCAPSULATED.format(
             MESSAGE_SPLIT=MESSAGE_SPLIT,
             **locals()
@@ -170,4 +175,7 @@ def verify(self, **kwargs):
         if format(pk, self.blockchain.prefix) != memo_key:
             raise InvalidMessageSignature
 
+        self.signed_by_account = account
+        self.signed_by_name = account["name"]
+
         return True