[docs] [issue25523] Correct "a" article to "an" article

Roundup Robot added the comment: New changeset 651f7addf4a8 by Martin Panter in branch '2.7': Issue #25523: Correct "a" article to "an" article https://hg.python.org/cpython/rev/651f7addf4a8 ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue25523> _______________________________________