[PyQt] PyQt5 NULL QVariant

[Matthias Kuhn]

Hi Phil
> No you're not. I can see that the loss of QPyNullVariant can be inconvenient when dealing with C++ code that makes significant use of Null QVariants. However adding it back would itself be a break in compatibility. I'm happy to consider that but it wouldn't be until PyQt v5.7 at the earliest - unless you can think of another solution?

Just wondering about the status of this. It's quite important for us to
be able to plan ahead.

 * Can we expect it with PyQt 5.7?
 * Could this theoretically be done with changes to sip only? That would
allow compatibility with older PyQt versions.
 * Could this be a wrapped QVariant instead of a PyQtNullVariant? (Just
proposing this in the hope this might result in a less hacky solution.
But anything that is not 0 or "" is fine with me.)

Thank you
Matthias