BUG19179711: Fix using '%s' in django backend

Currently it is not possible to escape '%s' in queries so,
'%s' is changed to '%S' which produces the same result for
both date and time formatting.

Author: peeyushgupta

lib/mysql/connector/django/base.py

@@ -283,7 +283,7 @@ def date_trunc_sql(self, lookup_type, field_name):
         The field_name is returned when lookup_type is not supported.
         """
         fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
-        format = ('%Y-', '%m', '-%d', ' %H:', '%i', ':%s')
+        format = ('%Y-', '%m', '-%d', ' %H:', '%i', ':%S')
         format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
         try:
             i = fields.index(lookup_type) + 1
@@ -323,7 +323,7 @@ def datetime_trunc_sql(self, lookup_type, field_name, tzname):
         else:
             params = []
         fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
-        format_ = ('%Y-', '%m', '-%d', ' %H:', '%i', ':%s')
+        format_ = ('%Y-', '%m', '-%d', ' %H:', '%i', ':%S')
         format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
         try:
             i = fields.index(lookup_type) + 1