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
to fix the grammar.
diff --git a/Doc/library/socket.rst b/Doc/library/socket.rst
index f79eba6..73b5d5c 100644
--- a/Doc/library/socket.rst
+++ b/Doc/library/socket.rst
@@ -757,7 +757,7 @@
Set blocking or non-blocking mode of the socket: if *flag* is 0, the socket is
set to non-blocking, else to blocking mode. Initially all sockets are in
blocking mode. In non-blocking mode, if a :meth:`recv` call doesn't find any
- data, or if a :meth:`send` call can't immediately dispose of the data, a
+ data, or if a :meth:`send` call can't immediately dispose of the data, an
:exc:`error` exception is raised; in blocking mode, the calls block until they
can proceed. ``s.setblocking(0)`` is equivalent to ``s.settimeout(0.0)``;
``s.setblocking(1)`` is equivalent to ``s.settimeout(None)``.