title: Restkit Response in text/xml
body: <p>I have a WS that return a plist.<br>
  I am using Restkit and I would like to map the response.</p>
  
  <p>So first I initilialize my ObjectManager like this:</p>
  
  <pre><code>sharedInstance.manager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:ROOT_URL]];
  </code></pre>
  
  <p>I accept the text/xml:</p>
  
  <pre><code>[[RKObjectManager sharedManager] setAcceptHeaderWithMIMEType:RKMIMETypeTextXML];
  </code></pre>
  
  <p>And I launch my request:</p>
  
  <pre><code>NSMutableURLRequest *request = [[RKObjectManager sharedManager] requestWithObject:nil method:RKRequestMethodPOST path:@"/foo/foo" parameters:nil];
  RKManagedObjectRequestOperation *operation = [[RKObjectManager sharedManager] managedObjectRequestOperationWithRequest:request managedObjectContext:[BddManager sharedInstance].manager.managedObjectStore.mainQueueManagedObjectContext success:^(RKObjectRequestOperation *operation, RKMappingResult *result) {
      NSLog(@"Loading mapping result: %d", result.count);
  } failure:^(RKObjectRequestOperation *operation, NSError *error) {
      NSLog(@"Fail!");
  }];
  [operation start];
  </code></pre>
  
  <p>Finally I get this error:</p>
  
  <pre><code>NSLocalizedDescription=Expected content type {(
  "application/x-www-form-urlencoded",
  "application/json"
  )}, got text/xml, 
  </code></pre>
  
  <p>What am I doing wrong?</p>