[New-bugs-announce] [issue28559] Unclear error message when raising wrong type of exceptions

[Dimitri Merejkowsky]

New submission from Dimitri Merejkowsky:

Motivation for the patch came from a tweet[1] of David Beazley:

def SomeError(Exception): 
    pass 

raise SomeError('blah')

(Note the `def` keyword instead of `class`):

If you run that, you get:

> TypeError: exceptions must derive from BaseException

Which is not very helpful.

Attached patch changes the error message to be:

> TypeError: exceptions must derive from BaseException, got NoneType

(By the way, it's very close to what Python2 used to say in this case)

----------
components: Interpreter Core
files: 0001-Fix-error-message-when-raising-with-the-wrong-type.patch
keywords: patch
messages: 279689
nosy: Dimitri Merejkowsky
priority: normal
severity: normal
status: open
title: Unclear error message when raising wrong type of exceptions
type: enhancement
versions: Python 3.7
Added file: http://bugs.python.org/file45267/0001-Fix-error-message-when-raising-with-the-wrong-type.patch

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue28559>
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