Move broadcast channel parts into trionics

tests/test_task_broadcasting.py

@@ -12,7 +12,7 @@ import pytest
 import trio
 from trio.lowlevel import current_task
 import tractor
-from tractor._broadcast import broadcast_receiver, Lagged
+from tractor.trionics import broadcast_receiver, Lagged
 
 
 @tractor.context
@@ -432,7 +432,6 @@ def test_first_recver_is_cancelled():
             tx, rx = trio.open_memory_channel(1)
             brx = broadcast_receiver(rx, 1)
             cs = trio.CancelScope()
-            sequence = list(range(3))
 
             async def sub_and_recv():
                 with cs:

tractor/_streaming.py

@@ -19,8 +19,8 @@ import trio
 from ._ipc import Channel
 from ._exceptions import unpack_error, ContextCancelled
 from ._state import current_actor
-from ._broadcast import broadcast_receiver, BroadcastReceiver
 from .log import get_logger
+from .trionics import broadcast_receiver, BroadcastReceiver
 
 
 log = get_logger(__name__)

tractor/trionics/__init__.py

@@ -3,8 +3,11 @@ Sugary patterns for trio + tractor designs.
 
 '''
 from ._mngrs import async_enter_all
+from ._broadcast import broadcast_receiver, BroadcastReceiver
 
 
 __all__ = [
     'async_enter_all',
+    'broadcast_receiver',
+    'BroadcastReceiver',
 ]