Error opening slave pty: No such file or directory

[prologic]

I successfully built pflask for uLinux and whilst the binary runs I get this error I'm not able to figure out (yet):

# pflask -- id
[✘] sysconf(): No error information
[✘] Error opening slave pty: No such file or directory
#

I don't understand from looking at the source code what master_fd is or what it's actually looking for and not finding?