On bug LP: #771719: it's said "Pressing the power button should not start the shutdown sequence once the installer has started writing files to the disk."
IMHO:
Option 1: "Remove / Hide power button as installer has started writing files to the disk".
Option 2: "Prompt user that system will in a no-working state if he insist to power down or reboot. So that user can decide what he really want."
On bug LP: #771719: it's said "Pressing the power button should not start the shutdown sequence once the installer has started writing files to the disk."
IMHO:
Option 1: "Remove / Hide power button as installer has started writing files to the disk".
Option 2: "Prompt user that system will in a no-working state if he insist to power down or reboot. So that user can decide what he really want."