Why would Putin move against North Korea? Russia, China and North Korea are long time allies. This should be seen as, exactly as the other fellow mentioned, an attempt to make South Korea dependent on its enemies for their gas supply.
Stay current. Russia and China are as much an allies as Hitler and Stalin during an interwar period.
And for Norks both Russia and China are decadent capitalist enemies.
Don’t get fooled by public posture of these nations. They are smiling at each other and carry a big stick.
The only reason why Russia writes off a Nork’s debt is because there is no chance to get it ever paid.