The multiple exception catch should be in a tuple.
diff --git a/Lib/csv.py b/Lib/csv.py
index 8511502..740efd5 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -389,7 +389,7 @@
                     try:
                         thisType(row[col])
                         break
-                    except ValueError, OverflowError:
+                    except (ValueError, OverflowError):
                         pass
                 else:
                     # fallback to length of string