Fix exception message (#1157)

Author: ikonst

docs/release_notes.rst

@@ -3,6 +3,15 @@
 Release Notes
 =============
 
+v5.3.5
+----------
+* Fix message of some exceptions derived from :class:`~pynamodb.exceptions.PynamoDBException` (#1113).
+
+Contributors to this release:
+
+* @pauliokas
+
+
 v5.3.4
 ----------
 * Make serialization :code:`null_check=False` propagate to maps inside lists (#1128).

pynamodb/__init__.py

@@ -7,4 +7,4 @@
 """
 __author__ = 'Jharrod LaFon'
 __license__ = 'MIT'
-__version__ = '5.3.4'
+__version__ = '5.3.5'

pynamodb/exceptions.py

@@ -8,11 +8,13 @@
 
 
 class PynamoDBException(Exception):
+    msg: str
+
     """
     A common exception class
     """
     def __init__(self, msg: Optional[str] = None, cause: Optional[Exception] = None) -> None:
-        self.msg = msg
+        self.msg = msg if msg is not None else self.msg
         self.cause = cause
         super(PynamoDBException, self).__init__(self.msg)
 

tests/test_exceptions.py

@@ -1,6 +1,6 @@
 from botocore.exceptions import ClientError
 
-from pynamodb.exceptions import PutError
+from pynamodb.exceptions import PynamoDBException, PutError
 
 
 def test_get_cause_response_code():
@@ -40,3 +40,10 @@ def test_get_cause_response_message__no_message():
     error = PutError()
     assert error.cause_response_message is None
 
+
+class PynamoDBTestError(PynamoDBException):
+    msg = "Test message"
+
+
+def test_subclass_message_is_not_overwritten_with_none():
+    assert PynamoDBTestError().msg == "Test message"