B904 from None check gets confused when class defined in except has a raise

[davidism]

In Werkzeug, we want to handle the case where Python was not compiled with SSL, so we try import ssl and define a placeholder class in except if the import fails. The class will raise for any attribute access. B904 gets confused and thinks it should be written raise ... from None even though that doesn't make sense here.

try:
    import ssl
except ImportError:

    class _SslDummy:
        def __getattr__(self, name: str) -> t.Any:
            raise RuntimeError("SSL support unavailable")  # noqa: B904

    ssl = _SslDummy()

Note that I had to add # noqa: B904 to the raise line.

[cooperlees]

In Werkzeug, we want to handle the case where Python was not compiled with SSL, so we try import ssl and define a placeholder class in except if the import fails. The class will raise for any attribute access. B904 gets confused and thinks it should be written raise ... from None even though that doesn't make sense here.

try:
    import ssl
except ImportError:

    class _SslDummy:
        def __getattr__(self, name: str) -> t.Any:
            raise RuntimeError("SSL support unavailable")  # noqa: B904

    ssl = _SslDummy()

Note that I had to add # noqa: B904 to the raise line.

I'm sure this is a dummy bit of code, but just making sure, please state in the RuntimeError a more descriptive error:

RuntimeError("SSL support unavailable with your build of python runtime. Please ensure you've compiled it in.")

[davidism]

That's the real code, copy pasted 😅 I did notice the message was a bit terse and will fix it.

[cooperlees]

That's the real code, copy pasted sweat_smile I did notice the message was a bit terse and will fix it.

I'm glad my dislike for vague error messages will possibly help someone one day understand this more easily!