better errors

modman/killthread.py

@@ -12,12 +12,12 @@ def killthread(thread, exc=KeyboardInterrupt):
 
     res = set_async_exc(ident, exc)
     if res == 0:
-        raise ValueError("thread id does not exist")
+        raise ValueError(f"thread {thread} does not exist")
     elif res > 1:
         # if return value is greater than one, you are in trouble.
         # you should call it again with exc=NULL to revert the effect.
         set_async_exc(ident, None)
-        raise SystemError("PyThreadState_SetAsyncExc failed")
+        raise SystemError(f"PyThreadState_SetAsyncExc on thread {thread} failed with return value {res}")