Add a specially handled `ContextCancelled` error

tractor/_exceptions.py

@@ -1,7 +1,7 @@
 """
 Our classy exception set.
 """
-from typing import Dict, Any, Optional, Type
+from typing import Dict, Any, Optional
 import importlib
 import builtins
 import traceback
@@ -18,7 +18,7 @@ class RemoteActorError(Exception):
     def __init__(
         self,
         message: str,
-        suberror_type: Optional[Type[BaseException]] = None,
+        suberror_type: Optional[Exception] = None,
         **msgdata
 
     ) -> None:
@@ -37,10 +37,6 @@ class InternalActorError(RemoteActorError):
     """
 
 
-class TransportClosed(trio.ClosedResourceError):
-    "Underlying channel transport was closed prior to use"
-
-
 class ContextCancelled(RemoteActorError):
     "Inter-actor task context cancelled itself on the callee side."
 
@@ -70,22 +66,19 @@ def pack_error(exc: BaseException) -> Dict[str, Any]:
 
 
 def unpack_error(
-
     msg: Dict[str, Any],
     chan=None,
     err_type=RemoteActorError
-
 ) -> Exception:
     """Unpack an 'error' message from the wire
     into a local ``RemoteActorError``.
-
     """
     error = msg['error']
 
     tb_str = error.get('tb_str', '')
     message = f"{chan.uid}\n" + tb_str
     type_name = error['type_str']
-    suberror_type: Type[BaseException] = Exception
+    suberror_type = Exception
 
     if type_name == 'ContextCancelled':
         err_type = ContextCancelled