some cleaning.

Author: tobiasraabe

src/pytask_parallel/execute.py

@@ -96,7 +96,7 @@ def pytask_execute_build(session: Session) -> bool | None:  # noqa: C901, PLR091
                     if not ready_tasks:
                         sleeper.increment()
 
-                    for task_name in running_tasks:
+                    for task_name in list(running_tasks):
                         future = running_tasks[task_name]
                         if future.done():
                             warning_reports, task_exception = future.result()
@@ -154,14 +154,10 @@ def pytask_execute_build(session: Session) -> bool | None:  # noqa: C901, PLR091
 
 
 def _parse_future_exception(
-    exception: BaseException | None,
+    exc: BaseException | None,
 ) -> tuple[type[BaseException], BaseException, TracebackType] | None:
-    """Parse a future exception."""
-    return (
-        None
-        if exception is None
-        else (type(exception), exception, exception.__traceback__)
-    )
+    """Parse a future exception into the format of ``sys.exc_info``."""
+    return None if exc is None else (type(exc), exc, exc.__traceback__)
 
 
 class ProcessesNameSpace: