[2.7] bpo-30157: Fix csv.Sniffer.sniff() regex pattern. (GH-5601) (GH-5604)

Co-authored-by: Jake Davis <jcdavis@awedge.net>.
(cherry picked from commit 2411292ba8155327125d8a1da8a4c9fa003d5909)
diff --git a/Lib/csv.py b/Lib/csv.py
index c155ada..70c53ae 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -217,7 +217,7 @@
         matches = []
         for restr in ('(?P<delim>[^\w\n"\'])(?P<space> ?)(?P<quote>["\']).*?(?P=quote)(?P=delim)', # ,".*?",
                       '(?:^|\n)(?P<quote>["\']).*?(?P=quote)(?P<delim>[^\w\n"\'])(?P<space> ?)',   #  ".*?",
-                      '(?P<delim>>[^\w\n"\'])(?P<space> ?)(?P<quote>["\']).*?(?P=quote)(?:$|\n)',  # ,".*?"
+                      '(?P<delim>[^\w\n"\'])(?P<space> ?)(?P<quote>["\']).*?(?P=quote)(?:$|\n)',   # ,".*?"
                       '(?:^|\n)(?P<quote>["\']).*?(?P=quote)(?:$|\n)'):                            #  ".*?" (no delim, no space)
             regexp = re.compile(restr, re.DOTALL | re.MULTILINE)
             matches = regexp.findall(data)