helper functions to get error code and message from response (#658)

.gitignore

@@ -60,6 +60,7 @@ cover/
 
 # PyCharm
 .idea/
+build/
 
 # Ignore Cache
 .cache/

pynamodb/exceptions.py

@@ -14,6 +14,14 @@ def __init__(self, msg=None, cause=None):
         self.cause = cause
         super(PynamoDBException, self).__init__(self.msg)
 
+    @property
+    def cause_response_code(self):
+        return getattr(self.cause, 'response', {}).get('Error', {}).get('Code')
+
+    @property
+    def cause_response_message(self):
+        return getattr(self.cause, 'response', {}).get('Error', {}).get('Message')
+
 
 class PynamoDBConnectionError(PynamoDBException):
     """

pynamodb/exceptions.pyi

@@ -4,6 +4,10 @@ class PynamoDBException(Exception):
     msg: str
     cause: Any
     def __init__(self, msg: Optional[Text] = ..., cause: Optional[Exception] = ...) -> None: ...
+    @property
+    def cause_response_code(self) -> Optional[str]: ...
+    @property
+    def cause_response_message(self) -> Optional[str]: ...
 
 class PynamoDBConnectionError(PynamoDBException): ...
 class DeleteError(PynamoDBConnectionError): ...

tests/test_exceptions.py

@@ -0,0 +1,42 @@
+from botocore.exceptions import ClientError
+
+from pynamodb.exceptions import PutError
+
+
+def test_get_cause_response_code():
+    error = PutError(
+        cause=ClientError(
+            error_response={
+                'Error': {
+                    'Code': 'hello'
+                }
+            },
+            operation_name='test'
+        )
+    )
+    assert error.cause_response_code == 'hello'
+
+
+def test_get_cause_response_code__no_code():
+    error = PutError()
+    assert error.cause_response_code is None
+
+
+def test_get_cause_response_message():
+    error = PutError(
+        cause=ClientError(
+            error_response={
+                'Error': {
+                    'Message': 'hiya'
+                }
+            },
+            operation_name='test'
+        )
+    )
+    assert error.cause_response_message == 'hiya'
+
+
+def test_get_cause_response_message__no_message():
+    error = PutError()
+    assert error.cause_response_message is None
+