Use "pdb" level logging in debug mode

tractor/_debug.py

@@ -276,7 +276,7 @@ def _set_trace(actor=None):
     pdb = _mk_pdb()
 
     if actor is not None:
-        log.runtime(f"\nAttaching pdb to actor: {actor.uid}\n")
+        log.pdb(f"\nAttaching pdb to actor: {actor.uid}\n")
 
         pdb.set_trace(
             # start 2 levels up in user code
@@ -306,7 +306,7 @@ breakpoint = partial(
 
 
 def _post_mortem(actor):
-    log.runtime(f"\nAttaching to pdb in crashed actor: {actor.uid}\n")
+    log.pdb(f"\nAttaching to pdb in crashed actor: {actor.uid}\n")
     pdb = _mk_pdb()
 
     # custom Pdb post-mortem entry

tractor/_root.py

@@ -86,6 +86,9 @@ async def open_root_actor(
         # for use of ``await tractor.breakpoint()``
         enable_modules.append('tractor._debug')
 
+        if loglevel is None:
+            loglevel = 'pdb'
+
     elif debug_mode:
         raise RuntimeError(
             "Debug mode is only supported for the `trio` backend!"