Increase the hacking version in test-requirements to match the
version used in the `designate` project.
This change fixes a few errors that the more recent `pyflakes` flags.
Change-Id: If7afefde0f33161016a27774021d27239c642eb5
Co-Authored-By: Michael Chapman <woppin@gmail.com>
Signed-off-by: Nicolas Bock <nicolas.bock@canonical.com>