Woops, fix `_post_mortem()` type sig..

We're passing a `extra_frames_up_when_async=2` now (from prior attempt
to hide `CancelScope.__exit__()` when `shield=True`) and thus both
`debug_func`s must accept it 🤦

On the brighter side found out that the `TypeError` from the call-sig
mismatch was actually being swallowed entirely so add some
`.exception()` msgs for such cases to at least alert the dev they broke
stuff XD

tractor/devx/_debug.py

@@ -808,33 +808,46 @@ async def _pause(
         Lock.repl = pdb
 
     try:
-        if debug_func is None:
+        # TODO: do we want to support using this **just** for the
+        # locking / common code (prolly to help address #320)?
+        #
+        # if debug_func is None:
             # assert release_lock_signal, (
             #     'Must pass `release_lock_signal: trio.Event` if no '
             #     'trace func provided!'
             # )
-            print(f"{actor.uid} ENTERING WAIT")
-            task_status.started(cs)
-
+            # print(f"{actor.uid} ENTERING WAIT")
             # with trio.CancelScope(shield=True):
             #     await release_lock_signal.wait()
 
-        else:
+        # else:
             # block here one (at the appropriate frame *up*) where
             # ``breakpoint()`` was awaited and begin handling stdio.
-            log.debug("Entering the synchronous world of pdb")
+        log.debug('Entering sync world of the `pdb` REPL..')
+        try:
             debug_func(
                 actor,
                 pdb,
                 extra_frames_up_when_async=2,
                 shield=shield,
             )
-            assert cs
+        except BaseException:
+            log.exception(
+                'Failed to invoke internal `debug_func = '
+                f'{debug_func.func.__name__}`\n'
+            )
+            raise
 
     except bdb.BdbQuit:
         Lock.release()
         raise
 
+    except BaseException:
+        log.exception(
+            'Failed to engage debugger via `_pause()` ??\n'
+        )
+        raise
+
 # XXX: apparently we can't do this without showing this frame
 # in the backtrace on first entry to the REPL? Seems like an odd
 # behaviour that should have been fixed by now. This is also why
@@ -905,14 +918,14 @@ async def pause(
 
             # NOTE: so the caller can always cancel even if shielded
             task_status.started(cs)
-            await _pause(
+            return await _pause(
                 debug_func=debug_func,
                 release_lock_signal=release_lock_signal,
                 shield=True,
                 task_status=task_status,
             )
     else:
-        await _pause(
+        return await _pause(
             debug_func=debug_func,
             release_lock_signal=release_lock_signal,
             shield=False,
@@ -1006,6 +1019,10 @@ _crash_msg: str = (
 def _post_mortem(
     actor: tractor.Actor,
     pdb: MultiActorPdb,
+    shield: bool = False,
+
+    # only for compat with `._set_trace()`..
+    extra_frames_up_when_async=0,
 
 ) -> None:
     '''
@@ -1034,7 +1051,7 @@ def _post_mortem(
 
 post_mortem = partial(
     pause,
-    _post_mortem,
+    debug_func=_post_mortem,
 )
 
 
@@ -1163,7 +1180,7 @@ async def maybe_wait_for_debugger(
                 with trio.CancelScope(shield=True):
                     await debug_complete.wait()
                 log.pdb(
-                    f'Child subactor released debug lock:'
+                    f'Child subactor released debug lock\n'
                     f'|_{in_debug}\n'
                 )