Fixed #14351 -- Modified the requests test case to avoid an timing problem in the test.

# Test cookie datetime expiration logic

>>> from datetime import datetime, timedelta

>>> import time

>>> delta = timedelta(seconds=10)

>>> response = HttpResponse()

>>> response.set_cookie('datetime', expires=datetime.utcnow()+delta)

>>> expires = datetime.utcnow() + delta

# There is a timing weakness in this test; The

# expected result for max-age requires that there be

# a very slight difference between the evaluated expiration

# time, and the time evaluated in set_cookie(). If this

# difference doesn't exist, the cookie time will be

# 1 second larger. To avoid the problem, put in a quick sleep,

# which guarantees that there will be a time difference.

>>> time.sleep(0.001)

>>> response.set_cookie('datetime', expires=expires)

>>> datetime_cookie = response.cookies['datetime']

>>> datetime_cookie['max-age']

10