Use ResponseStatusException in ArticleController

src/main/kotlin/com/example/blog/HttpControllers.kt

@@ -1,6 +1,8 @@
 package com.example.blog
 
+import org.springframework.http.HttpStatus.*
 import org.springframework.web.bind.annotation.*
+import org.springframework.web.server.ResponseStatusException
 
 @RestController
 @RequestMapping("/api/article")
@@ -11,7 +13,7 @@ class ArticleController(private val repository: ArticleRepository) {
 
 	@GetMapping("/{slug}")
 	fun findOne(@PathVariable slug: String) =
-			repository.findBySlug(slug) ?: throw IllegalArgumentException("Wrong article slug provided")
+			repository.findBySlug(slug) ?: throw ResponseStatusException(NOT_FOUND, "Wrong article slug provided")
 
 }