Move exc state to generator. Fixes bpo-25612 (#1773)

Move exception state information from frame objects to coroutine (generator/thread) object where it belongs.

Lib/test/test_exceptions.py

@@ -1097,6 +1097,62 @@ class ExceptionTests(unittest.TestCase):
                     self.assertIn("test message", report)
                 self.assertTrue(report.endswith("\n"))
 
+    def test_yield_in_nested_try_excepts(self):
+        #Issue #25612
+        class MainError(Exception):
+            pass
+
+        class SubError(Exception):
+            pass
+
+        def main():
+            try:
+                raise MainError()
+            except MainError:
+                try:
+                    yield
+                except SubError:
+                    pass
+                raise
+
+        coro = main()
+        coro.send(None)
+        with self.assertRaises(MainError):
+            coro.throw(SubError())
+
+    def test_generator_doesnt_retain_old_exc2(self):
+        #Issue 28884#msg282532
+        def g():
+            try:
+                raise ValueError
+            except ValueError:
+                yield 1
+            self.assertEqual(sys.exc_info(), (None, None, None))
+            yield 2
+
+        gen = g()
+
+        try:
+            raise IndexError
+        except IndexError:
+            self.assertEqual(next(gen), 1)
+        self.assertEqual(next(gen), 2)
+
+    def test_raise_in_generator(self):
+        #Issue 25612#msg304117
+        def g():
+            yield 1
+            raise
+            yield 2
+
+        with self.assertRaises(ZeroDivisionError):
+            i = g()
+            try:
+                1/0
+            except:
+                next(i)
+                next(i)
+
 
 class ImportErrorTests(unittest.TestCase):