set method doesn't include user set timestamp if update set() is supposed to update the record with the key if it already exists. It does update the value marshalled data blob. However it doesn't update the timestamp column for rdbms tables if provided. This change updates the x_time column with the provided __timestamp or preserves the original timestamp.

#!/usr/bin/env python

# Roundup requires Python 2.7+ as mentioned in doc\installation.txt
from __future__ import print_function
import sys

VERSION_NEEDED = (2, 7)

if sys.version_info < VERSION_NEEDED:
    print("Content-Type: text/plain\n")
    print("Roundup requires Python %s.%s or newer." % VERSION_NEEDED)
    sys.exit(0)