make GreenletExit a subclass of BaseException but not Exception

gevent/hub.py

@@ -35,6 +35,15 @@ except ImportError:
 getcurrent = greenlet.getcurrent
 GreenletExit = greenlet.GreenletExit
 
+
+# In greenlet >= 0.3.2, GreenletExit is a subclass of BaseException
+# In greenlet <= 0.3.1, GreenletExit is a subclass of Exception
+# Since, GreenletExit is a part of gevent's public interface, we want
+# it to be consistent, so if we got older greenlet, we monkey patch
+# GreenletExit's __bases__
+if GreenletExit.__bases__[0] is Exception:
+    GreenletExit.__bases__ = (BaseException, )
+
 if sys.version_info[0] <= 2:
     thread = __import__('thread')
 else: