ENH: Added video file exists check
Merge branch 'master' of https://github.com/isolver/psychopy
Merge branch 'master' of https://github.com/isolver/psychopy
Merge branch 'master' of https://github.com/isolver/psychopy
Merge branch 'master' of https://github.com/isolver/psychopy
Merge branch 'master' of https://github.com/isolver/psychopy
BF: iohub kb keys on linux
- mods now labeled correctly
- control keys OK

Numlock key and char values need to be sorted out; inconsitant mapping with other OS's