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/difflib.rst b/Doc/library/difflib.rst
index ead6b7a..c6bf3ef 100644
--- a/Doc/library/difflib.rst
+++ b/Doc/library/difflib.rst
@@ -276,7 +276,7 @@
generating the delta lines) in unified diff format.
Unified diffs are a compact way of showing just the lines that have changed plus
- a few lines of context. The changes are shown in a inline style (instead of
+ a few lines of context. The changes are shown in an inline style (instead of
separate before/after blocks). The number of context lines is set by *n* which
defaults to three.