fix(agent): log exception instead of returning (revert #121)

We need to keep backward compatibility with older clients and they will
have trouble unpickling a new exception, as we are sending these out
pickled by reference and not by value (solving that would require
serialization backend specific actions, which I would rather avoid
for now to unblock a release).

src/isolate/connections/grpc/agent.py

@@ -10,7 +10,6 @@
 from dataclasses import dataclass
 from typing import (
     Any,
-    Generator,
     Iterable,
     Iterator,
 )
@@ -66,7 +65,7 @@ def Run(
                         self.log(
                             "The setup function has thrown an error. Aborting the run."
                         )
-                        yield from self.send_object(
+                        yield self.send_object(
                             request.setup_func.method,
                             result,
                             was_it_raised,
@@ -87,7 +86,7 @@ def Run(
                 "function",
                 extra_args=extra_args,
             )
-            yield from self.send_object(
+            yield self.send_object(
                 request.function.method,
                 result,
                 was_it_raised,
@@ -113,8 +112,11 @@ def execute_function(
             # NOTE: technically any sort of exception could be raised here, since
             # depickling is basically involves code execution from the *user*.
             function = from_grpc(function)
-        except BaseException as exc:
-            return exc, True, traceback.format_exc()
+        except BaseException:
+            self.log(traceback.format_exc())
+            raise AbortException(
+                f"The {function_kind} function could not be deserialized."
+            )
 
         if not callable(function):
             raise AbortException(
@@ -143,7 +145,7 @@ def send_object(
         result: object,
         was_it_raised: bool,
         stringized_tb: str | None,
-    ) -> Generator[definitions.PartialRunResult, None, Any]:
+    ) -> definitions.PartialRunResult:
         try:
             definition = serialize_object(serialization_method, result)
         except SerializationError:
@@ -166,7 +168,7 @@ def send_object(
             was_it_raised=was_it_raised,
             stringized_traceback=stringized_tb,
         )
-        yield definitions.PartialRunResult(
+        return definitions.PartialRunResult(
             result=serialized_obj,
             is_complete=True,
             logs=[],