asyncio: sync with Tulip, add a new asyncio.coroutines module

Lib/asyncio/locks.py

@@ -6,7 +6,7 @@
 
 from . import events
 from . import futures
-from . import tasks
+from .coroutines import coroutine
 
 
 class _ContextManager:
@@ -112,7 +112,7 @@ def locked(self):
         """Return True if lock is acquired."""
         return self._locked
 
-    @tasks.coroutine
+    @coroutine
     def acquire(self):
         """Acquire a lock.
 
@@ -225,7 +225,7 @@ def clear(self):
         to true again."""
         self._value = False
 
-    @tasks.coroutine
+    @coroutine
     def wait(self):
         """Block until the internal flag is true.
 
@@ -278,7 +278,7 @@ def __repr__(self):
             extra = '{},waiters:{}'.format(extra, len(self._waiters))
         return '<{} [{}]>'.format(res[1:-1], extra)
 
-    @tasks.coroutine
+    @coroutine
     def wait(self):
         """Wait until notified.
 
@@ -306,7 +306,7 @@ def wait(self):
         finally:
             yield from self.acquire()
 
-    @tasks.coroutine
+    @coroutine
     def wait_for(self, predicate):
         """Wait until a predicate becomes true.
 
@@ -402,7 +402,7 @@ def locked(self):
         """Returns True if semaphore can not be acquired immediately."""
         return self._value == 0
 
-    @tasks.coroutine
+    @coroutine
     def acquire(self):
         """Acquire a semaphore.