One way of telling that your snake could be constipated is by looking at where the vent is, they start looking very round or thicker than normal. And like you have already been told a warm water bath usually does the trick. As you see if did. The other way to know if your snake is constipated is to feel the snake you can actually feel the poop not squeezing the snake at all because you can injure you snake just run your hand down the snake you can feel the mass its gross. Glad your snake took a poo, it happens sometimes, but you may want to check the humidity there has to be a certain amount of humidity or they will tend to become dehydrated causing the constipation. Sorry I'm long winded.