AFNetworking版本2内容类型错误

我正在尝试制作一个与特定JIRA服务器交互的iPhone应用程序.我有以下代码登录:

NSURL *url = [[NSURL alloc] initWithString:@"https://mycompany.atlassian.net/rest/auth/latest/session/"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];
NSString *postString = [NSString stringWithFormat:@"{\"username\":\"%@\",\"password\":\"%@\"}", username, password];
[request setHTTPBody:[postString dataUsingEncoding:NSUTF8StringEncoding]];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[request setValue:@"application/json" forHTTPHeaderField:@"Accept" ];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:
    ^(AFHTTPRequestOperation *operation, id responseObject) {
        NSLog(@"JSON: %@", responseObject);
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"ERROR: %@", error);

    }
 ];
 [operation start];

但它给了我以下与Content-Type有关的错误:

ERROR: Error Domain=AFNetworkingErrorDomain Code=-1011
"Request failed: unsupported media type (415)"
UserInfo=0x8cd6540
{
  NSErrorFailingURLKey=https://mycompany.atlassian.net/rest/auth/latest/session/,
  NSLocalizedDescription=Request failed: unsupported media type (415),
  NSUnderlyingError=0x8c72e70
  "Request failed: unacceptable content-type: text/html", 

我不确定问题是什么.我发现这个问题,我认为可能是一个类似的问题,但答案是要么使用AFJSONRequestOperation该类(我不能,因为我使用AFNetworking版本2,没有该类),或修复它在服务器端(我也不能出于显而易见的原因).

当我无法修复服务器端而无法使用时,我可以修复此错误AFJSONRequestOperation？