Internal use of JsonKeysetWriter, which is deprecated

[ahyatt-continua]

At _json_proto_keyset_format.py:83 (in my 1.10 Python Tink, and also in your repository in HEAD), you use JsonKeysetWriter, which is deprecated.

I don't think a library should be printing out deprecation warnings about internal usage of deprecated functions, since users have no way of fixing it.

Also, it's a bit worrying: is the deprecation something I, as a user, need to be concerned about?

I think either fixing the use (using the replacement suggested in the JsonKeysetWriter class), or simply removing the warning would be a good fix for this issue.

[juergw]

I agree, I removed the warning.

[juergw]

Here: 71752ea