make the debug-watchman option to runtests.py work on Python 3
make the debug-watchman option to runtests.py work on Python 3

Summary: This is a silly `input` vs `raw_input` difference.

Reviewed By: wez

Differential Revision: D4351504

fbshipit-source-id: b733f4148e96c72baadc5e9638ac2440d5b3a5cf

kwlzn/watchman,wez/watchman,wez/watchman,wez/watchman,nodakai/watchman,wez/watchman,wez/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,wez/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,kwlzn/watchman,nodakai/watchman,nodakai/watchman,nodakai/watchman,nodakai/watchman,wez/watchman,kwlzn/watchman,wez/watchman,kwlzn/watchman,wez/watchman,facebook/watchman,kwlzn/watchman,nodakai/watchman,nodakai/watchman,kwlzn/watchman,kwlzn/watchman,nodakai/watchman