add test__real_greenlet.py

greentest/test__real_greenlet.py

+"""Testing that greenlet restores sys.exc_info.
+
+Passes with CPython + greenlet 0.4.0
+
+Fails with PyPy 2.2.1
+"""
+import sys
+import greenlet
+
+
+print ('Your greenlet version: %s' % (getattr(greenlet, '__version__', None), ))
+
+
+result = []
+
+
+def func():
+    result.append(repr(sys.exc_info()))
+
+
+g = greenlet.greenlet(func)
+try:
+    1 / 0
+except ZeroDivisionError:
+    g.switch()
+
+
+assert result == ['(None, None, None)'], result