use getcurrent directly and not through the module

gevent/hub.py

@@ -237,7 +237,7 @@ class Waiter(object):
         """Wake up the greenlet that is calling wait() currently (if there is one).
         Can only be called from Hub's greenlet.
         """
-        assert greenlet.getcurrent() is get_hub(), "Can only use Waiter.switch method from the mainloop"
+        assert getcurrent() is get_hub(), "Can only use Waiter.switch method from the mainloop"
         if self.greenlet is not None:
             try:
                 self.greenlet.switch(value)
@@ -248,7 +248,7 @@ class Waiter(object):
         """Make greenlet calling wait() wake up (if there is a wait()).
         Can only be called from Hub's greenlet.
         """
-        assert greenlet.getcurrent() is get_hub(), "Can only use Waiter.switch method from the mainloop"
+        assert getcurrent() is get_hub(), "Can only use Waiter.switch method from the mainloop"
         if self.greenlet is not None:
             try:
                 self.greenlet.throw(*throw_args)
@@ -260,7 +260,7 @@ class Waiter(object):
         """Wait until switch() or throw() is called.
         """
         assert self.greenlet is None, 'This Waiter is already used by %r' % (self.greenlet, )
-        self.greenlet = greenlet.getcurrent()
+        self.greenlet = getcurrent()
         try:
             return get_hub().switch()
         finally: