Corrections for a/an in code comments and documentation
diff --git a/Lib/test/test_imageop.py b/Lib/test/test_imageop.py
index 9589bf2..50ad4e7 100644
--- a/Lib/test/test_imageop.py
+++ b/Lib/test/test_imageop.py
@@ -121,7 +121,7 @@
         print 'grey2rgb'
     image = imageop.grey2rgb(greyimage, width, height)
 
-    # Convert a 8-bit deep greyscale image to a 1-bit deep image by
+    # Convert an 8-bit deep greyscale image to a 1-bit deep image by
     # thresholding all the pixels. The resulting image is tightly packed
     # and is probably only useful as an argument to mono2grey.
     if verbose: