Keypress clock fix

[lawhead]

Overview

Fix a bug in the task helper get_key_press method introduced by recent changes to the experiment clock.

Ticket

https://www.pivotaltracker.com/story/show/179628895

Contributions

• Refactored get_key_press to convert the timestamp after it is retrieved from psychopy.

Test

• Run Copy Phrase with the Inquiry Preview feature. The keypress should not throw an exception. The stamp associated with the keypress in the triggers.txt file should have a value greater than the preceding inquiry_preview trigger and less than the fixation trigger.

Documentation

• Are documentation updates required? In-line, README, or documentation? Verify the updates you did here.