kubectl delete command: adding labelSelector

Add a Visitor pattern on top of ResourcesFromArgs

Allows ResourcesFromArgs to return an opaque list of items and have client
commands react to them.

Change request.go to return apiserver errors for arbitrary status codes to
better respond to generic actions that don't make sense (kubectl delete operations foo)

pkg/client/request.go

@@ -411,11 +411,26 @@ func (r *Request) transformResponse(resp *http.Response, req *http.Request) ([]b
 	switch {
 	case resp.StatusCode < http.StatusOK || resp.StatusCode > http.StatusPartialContent:
 		if !isStatusResponse {
-			return nil, false, &UnexpectedStatusError{
+			var err error = &UnexpectedStatusError{
 				Request:  req,
 				Response: resp,
 				Body:     string(body),
 			}
+			// TODO: handle other error classes we know about
+			switch resp.StatusCode {
+			case http.StatusConflict:
+				if req.Method == "POST" {
+					// TODO: add Resource() and ResourceName() as Request methods so that we can set these
+					err = errors.NewAlreadyExists("", "")
+				} else {
+					err = errors.NewConflict("", "", err)
+				}
+			case http.StatusNotFound:
+				err = errors.NewNotFound("", "")
+			case http.StatusBadRequest:
+				err = errors.NewBadRequest(err.Error())
+			}
+			return nil, false, err
 		}
 		return nil, false, errors.FromObject(&status)
 	}