bpo-30157: Fix csv.Sniffer.sniff() regex pattern. (GH-5601) (GH-5602)

Co-authored-by: Jake Davis <jcdavis@awedge.net>
(cherry picked from commit 2411292ba8155327125d8a1da8a4c9fa003d5909)
diff --git a/Misc/ACKS b/Misc/ACKS
index 4c8b86a..b31190c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -355,6 +355,7 @@
 Jonathan Dasteel
 Pierre-Yves David
 A. Jesse Jiryu Davis
+Jake Davis
 Ratnadeep Debnath
 Merlijn van Deen
 John DeGood
diff --git a/Misc/NEWS.d/next/Library/2018-02-09-14-44-43.bpo-30157.lEiiAK.rst b/Misc/NEWS.d/next/Library/2018-02-09-14-44-43.bpo-30157.lEiiAK.rst
new file mode 100644
index 0000000..9f65193
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-02-09-14-44-43.bpo-30157.lEiiAK.rst
@@ -0,0 +1,2 @@
+Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last
+field is quoted.  Patch by Jake Davis.