Recurse into all the ancestors when checking if an object is an exception

Since we were going only into the first level, we weren't inferring when a class used a metaclass which defined a base Exception class for the aforementioned class.

Author: PCManticore

pylint/checkers/utils.py

@@ -430,7 +430,7 @@ def inherit_from_std_ex(node):
  and node.root().name == EXCEPTIONS_MODULE:
  return True
  return any(inherit_from_std_ex(parent)
- for parent in node.ancestors(recurs=False))
+ for parent in node.ancestors(recurs=True))
 
 def error_of_type(handler, error_type):
  """

pylint/test/functional/invalid_exceptions_caught.py

@@ -1,8 +1,8 @@
-"""Test for catching non-exceptions."""
+# pylint: disable=missing-docstring, too-few-public-methods
 # pylint: disable=too-many-ancestors, no-absolute-import, import-error, multiple-imports,wrong-import-position
 from __future__ import print_function
 
-import socket, binascii
+import socket, binascii, abc, six
 
 class MyException(object):
  """Custom 'exception'."""
@@ -107,3 +107,17 @@ class SecondSkipException(SkipException):
  1 + 42
 except range: # [catching-non-exception]
  print('caught')
+
+
+class HasErrorInMRO(six.with_metaclass(abc.ABCMeta, Exception)):
+ pass
+
+
+class Second(HasErrorInMRO):
+ pass
+
+
+try:
+ raise Second
+except Second:
+ pass