Issue #25523: Correct "a" article to "an" article

This changes the main documentation, doc strings, source code comments, and a
couple error messages in the test suite. In some cases the word was removed
or edited some other way to fix the grammar.

1 files changed, 1 insertions, 1 deletions

diff --git a/Lib/io.py b/Lib/io.py
index 8d68f1e424..e03db97e4d 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -19,7 +19,7 @@ streams. BytesIO is a simple stream of in-memory bytes.
 Another IOBase subclass, TextIOBase, deals with the encoding and decoding
 of streams into text. TextIOWrapper, which extends it, is a buffered text
 interface to a buffered raw stream (`BufferedIOBase`). Finally, StringIO
-is a in-memory stream for text.
+is an in-memory stream for text.
 
 Argument names are not part of the specification, and only the arguments
 of open() are intended to be used as keyword arguments.