import "greenlet" first, then "py.magic.greenlet"

the former is default now

gevent/hub.py

@@ -20,9 +20,12 @@ __all__ = ['getcurrent',
 
 
 try:
-    from py.magic import greenlet
-except ImportError:
     greenlet = __import__('greenlet').greenlet
+except ImportError:
+    try:
+        from py.magic import greenlet
+    except ImportError:
+        raise ImportError('gevent requires greenlet library: http://pypi.python.org/pypi/greenlet/')
 
 getcurrent = greenlet.getcurrent
 GreenletExit = greenlet.GreenletExit