Почему выдает ошибку: 1062, u"Duplicate entry 'pbkdf2:sha256:50000$' for key 'user_password'"?

# read the posted value
    _name = request.form['inputName']
    _email = request.form['inputEmail']
    _password = request.form['inputPassword']

    # validate values
    if _name and _email and _password:
        # let's go
        conn = mysql.connect()
        cursor = conn.cursor()
        _hashed_password = generate_password_hash(_password)
        cursor.callproc('sp_createUser', (_name, _email, _hashed_password))
        data = cursor.fetchall()

        if (len(data) is 0): 
            conn.commit()
            return json.dumps({'message': 'User created successfully !'})
        else:
            return json.dumps({'error': str(data[0])})