@boukeversteegh can you please re-trigger the 3.6 build please? Not sure why it is failing on the CI, local tests pass.

@abn I've rerun the tests, and this time there are some more detailed errors being shown.

Perhaps we need to extend both ABC and IProtoMessage?

I suspect it is an issue with the dataclasses backport implementation for 3.6. I am curious why local tests ran okay for 3.6. Will look at it soon.

@boukeversteegh seems that by fixing the inheritence we corrected a code path that triggered a python 3.6 compatibility issue. As mentioned above, looks like the issue has to do with subtle differences between dataclasses and dataclasses backport.

@nat-n @boukeversteegh I have updated the fix to appraoch it a bit differently; rather than changing the inheritence I have now changed the type hinting so that it explicitly suggests betterproto.Message child class or something that implements the protocol grpclib._typing.IProtoMessage. For now, this fixes the issue.

Thanks for the changes, this looks good now.