call next() the right way (#4804)

superset/db_engine_specs.py

@@ -869,7 +869,7 @@ def create_table_from_csv(form, table):
         """Uploads a csv file and creates a superset datasource in Hive."""
         def get_column_names(filepath):
             with open(filepath, 'rb') as f:
-                return unicodecsv.reader(f, encoding='utf-8-sig').next()
+                return next(unicodecsv.reader(f, encoding='utf-8-sig'))
 
         table_name = form.name.data
         filename = form.csv_file.data.filename