Bug 16376: (regression tests)

Bug 16376: (regression tests)

This patch introduces a regression test for exception_holidays. This routine
returns a list of datetimes to be used in date comparison and some datetimes don't exist
in some timezones, so floating timezones should be used instead.

To test:
- Apply the patch on master
- Run:
  $ prove t/db_dependent/Holidays.t
=> FAIL: The new test fails

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>