Sorry for the delay in responding. Just wanted to check in and note that the osmocom OP25 repo now has a patch for building OP25 with python3/gnuradio3.8. Additionally, the principal python apps (rx.py, multi_rx.py et al). have been rewritten to run under either python 2 or 3.
So far after clearing away several nitpicks related to python3 everything appears to be solid.
Also it should be noted that the 'max' branch of the osmocom OP25 repo has been deprecated and is slated to be deleted at some point. Going forward all new commits will be made directly to the 'master' branch - this also includes the gr3.8 patch.
Please report any problems esp. with but not limited to these modifications...
Max