Check $PATH for the stty executable

[earldouglas]

The code currently expects stty to be in /bin/stty. This is not always the case (e.g. in NixOS, it's in /run/current-system/sw/bin/stty), which can lead to the following error on login:

Password (typing will be hidden): 
 ▸    failed turning off console echo for password entry:
 ▸      no such file or directory

[ransombriggs]

Replicated your problem and am working on a fix.

[ransombriggs]

I have a fix ready, I should be able to ship it out later today after it is reviewed / released.

[ransombriggs]

I just verified my fix locally, could you please run heroku update and try again?

[earldouglas]

Works for me, thanks!