Backport of r67908:
Added test case to ensure attempts to read from a file opened for writing
fail.
diff --git a/Lib/test/test_file.py b/Lib/test/test_file.py
index 8308710..f678df6 100644
--- a/Lib/test/test_file.py
+++ b/Lib/test/test_file.py
@@ -116,6 +116,8 @@
         except:
             self.assertEquals(self.f.__exit__(*sys.exc_info()), None)
 
+    def testReadWhenWriting(self):
+        self.assertRaises(IOError, self.f.read)
 
 class OtherFileTests(unittest.TestCase):