PTY not working in Mintty

[Pavel Fedin]

  Hello everyone!

  I have two machines in my posession: a desktop and a laptop. Both 
machines have Windows 10 and the same up to date version of Cygwin 
installed. The only difference is "age". The laptop is a new one, with 
freshly installed OS and Cygwin, and the desktop is about one year old 
and its hard drive is about 10 years old, Cygwin was installed a while 
ago and periodically upgraded.

  So far, on the desktop PTY does not work. Attempt to run docker (i am 
using Docker Desktop for Windows) causes "Terminal is not a PTY" error, 
i have to use winpty wrapper as suggested. On the laptop everything is 
fine, docker works in MinTTY out of the box with no need for winpty.

  Is there maybe some hidden setting, which got stuck somewhere in the 
older system ? Why is PTY not working? Can anyone help me to diagnose that ?