Mastermind is a code-breaking game for two players where people try to guess the opponents guesses. You can find the detail on wikipedia.
The game you play with your friend is a little different, a type of mastermind with using all digits available ($0-9$) with $4$ digit numbers.
Your friend keeps a $4$ digit number (all digits are distinct) and you try to guess it as below:
5178 0 -2 9017 +1 -1 4879 +1 -1 9128 +1 -2 1704 0 -2
After getting these keys (+,-) you notice that something is wrong with the keys. After telling this to your friend, your friend rechecked the information he gave and then notice one of the keys he provided is wrong and he tells you that you can still find it without that guess and the keys with it.
Which guess is wrong and what is the number your friend kept?