fix outdated comments in asyncio (#121783)

Lib/asyncio/futures.py

@@ -43,7 +43,6 @@ class Future:
     - This class is not compatible with the wait() and as_completed()
       methods in the concurrent.futures package.
 
-    (In Python 3.4 or later we may be able to unify the implementations.)
     """
 
     # Class variables serving as defaults for instance variables.
@@ -61,7 +60,7 @@ class Future:
     #   the Future protocol (i.e. is intended to be duck-type compatible).
     #   The value must also be not-None, to enable a subclass to declare
     #   that it is not compatible by setting this to None.
-    # - It is set by __iter__() below so that Task._step() can tell
+    # - It is set by __iter__() below so that Task.__step() can tell
     #   the difference between
     #   `await Future()` or`yield from Future()` (correct) vs.
     #   `yield Future()` (incorrect).

Lib/asyncio/tasks.py

@@ -281,7 +281,7 @@ class Task(futures._PyFuture):  # Inherit Python Task implementation
     def __step(self, exc=None):
         if self.done():
             raise exceptions.InvalidStateError(
-                f'_step(): already done: {self!r}, {exc!r}')
+                f'__step(): already done: {self!r}, {exc!r}')
         if self._must_cancel:
             if not isinstance(exc, exceptions.CancelledError):
                 exc = self._make_cancelled_error()
@@ -379,7 +379,7 @@ class Task(futures._PyFuture):  # Inherit Python Task implementation
         else:
             # Don't pass the value of `future.result()` explicitly,
             # as `Future.__iter__` and `Future.__await__` don't need it.
-            # If we call `_step(value, None)` instead of `_step()`,
+            # If we call `__step(value, None)` instead of `__step()`,
             # Python eval loop would use `.send(value)` method call,
             # instead of `__next__()`, which is slower for futures
             # that return non-generator iterators from their `__iter__`.

Modules/_asynciomodule.c

@@ -2892,7 +2892,7 @@ task_step_impl(asyncio_state *state, TaskObj *task, PyObject *exc)
 
     if (task->task_state != STATE_PENDING) {
         PyErr_Format(state->asyncio_InvalidStateError,
-                     "_step(): already done: %R %R",
+                     "__step(): already done: %R %R",
                      task,
                      exc ? exc : Py_None);
         goto fail;