title: [Swift, Alamofire]: responseValidationFailed with error code 400
body: <p>My problem is basically in the title. The code that I am trying to run is just below. VVV</p>
  
  <pre><code>let unfollow = "https://api.instagram.com/v1/users/\(userID)/relationship?access_token=\(access_token)&amp;action=unfollow"
  
      Alamofire.request(unfollow, method: .post).validate().responseJSON(completionHandler: {
          response in
  
          switch response.result {
  
          case .success(let value):
  
              let data = JSON(value)["data"]
              print(data["outgoing_status"].stringValue)
  
          case .failure(let error):
              print(error)
  
          }
  
      })
  </code></pre>
  
  <p>The exact console error I recieve is: <code>responseValidationFailed(Alamofire.AFError.ResponseValidationFailureReason.unacceptableStatusCode(400))</code></p>
  
  <p>I am using the Instagram API by the way but I don't think that that is necessarily related to the issue.</p>
  
  <p>Any help greatly appreciated.</p>