Map `breakpoint()` built-in to new `.pause_from_sync()` ep

tractor/_root.py

@@ -90,7 +90,7 @@ async def open_root_actor(
     # https://github.com/python-trio/trio/issues/1155#issuecomment-742964018
     builtin_bp_handler = sys.breakpointhook
     orig_bp_path: str | None = os.environ.get('PYTHONBREAKPOINT', None)
-    os.environ['PYTHONBREAKPOINT'] = 'tractor._debug._set_trace'
+    os.environ['PYTHONBREAKPOINT'] = 'tractor._debug.pause_from_sync'
 
     # attempt to retreive ``trio``'s sigint handler and stash it
     # on our debugger lock state.
@@ -237,10 +237,10 @@ async def open_root_actor(
             ) as err:
 
                 entered = await _debug._maybe_enter_pm(err)
-
                 if (
                     not entered
-                    and not is_multi_cancelled(err)
+                    and
+                    not is_multi_cancelled(err)
                 ):
                     logger.exception('Root actor crashed:\n')