Redmine

Hello,
I try to use python to create a project, but it always return "HTTP Error 422: Unprocessable Entity", here are my python codes which can get all kinds of redmine data if data is None, is there something wrong?

headers = {'Content-Type': 'application/json',
                   "X-Redmine-API-Key" : "62ab473dec64ebc3d9514b0176f1f2f4a66e298c"}
data = json.dumps({"is_public": false, "identifier": "test", "name": "test"})
request = urllib2.Request(url=url, headers=headers, data=data)
response = urllib2.urlopen(request, timeout=5)
result = json.load(response)

And I try to use curl in terminal like this:

curl -v -H "Content-Type: application/json" -H "X-Redmine-API-Key: 62ab473dec64ebc3d9514b0176f1f2f4a66e298c" -X POST --data "{\"identifier\": \"test\", \"name\": \"test\"}" localhost:3000/redmine/projects.json

it responded, but always return name blank error, however, my data contained name and identifier indeed, why they were not recognized?

{"errors":["Name cannot be blank","Identifier cannot be blank","Identifier is too short (minimum is 1 characters)"]}

My redmine information

Environment:
  Redmine version                3.3.0.stable
  Ruby version                   2.1.10-p492 (2016-04-01) [x86_64-linux]
  Rails version                  4.2.6
  Environment                    production
  Database adapter               Mysql2

Thanks in advance.