That error is because Poser 12 uses a newer version of Python. None of the old Poser scripts work. (Though some are being fixed.)

DSON doesn't work with Poser 12, and DAZ doesn't seem interested in updating it. There's more information in the Poser 12 forum. Basically, if you want to use DSON, use an earlier version of Poser.

If you just want to get rid of the error message, there's some information here:

https://www.renderosity.com/rr/mod/forumpro/?thread_id=2954988

You can set things up so you can still use DSON in Poser 11, and won't get error messages in Poser 12.