Improve test coverage.  Hope the test_file changes work the same on windows.
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index cb7e992..48c9674 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -1589,6 +1589,11 @@
   ...
 ValueError: 7
 
+>>> f().throw("abc")     # throw on just-opened generator
+Traceback (most recent call last):
+  ...
+TypeError: exceptions must be classes, or instances, not str
+
 
 Now let's try closing a generator: