Revise "This is probably not a problem with npm." error

This might be a trivial idea but every time I come across the error “This is probably not a problem with npm” the language irks me. It’s either a problem with npm or it’s not-- the use of ‘probably’ leaves a user scratching their head. Either be definitive or leave it out of error logging.

I’m trying to solve an issue not read a mystery novel.