I had exactly the same problem with sublimeT3. First on a terminal I ran the next command:
And the output was an empty line.
Next I ran:
An this was the output:
I tried to reset the locales with some of the answers given here, but everything was unsuccessful, every time the "locale" command gave the same output.
Even my /etc/default/locale seemed to be right:
Because of this I wondered if maybe something was overriding the environment variables. My .pam_environment file seemed to be correct:
So I ran the next command which gave me the clue of what was going on:
$cat .bashrc | grep LANG
Here the output:
I don't know when or how, but I ended up with two lines on my .bashrc that overrode the value of "locale" variables. I'm not pasting the whole bash file, but the two key lines were these:
By commenting them on the bash file and a reboot, voila! my locale was set up as it was intended to, and sublimeT3 stopped complaining. It's been more than a year since this was formulated, but maybe it could help someone else!