目录结构：
Interface
/common
/datas
/Log
/report
/TestCase
RunTest.py
我的数据源是 yaml 格式，获取 yaml 格式的代码如下：

# -*- coding: UTF-8 -*-
import yaml
import os


class ReadYaml(object):
    def __init__(self):
        yaml_path = "../datas/TestData.yaml"
        with open(yaml_path, "r") as f:
            self.content = yaml.load(f)

RunTest.py 代码

# -*- coding:UTF-8 -*-
import os
import unittest
import time
from common import HTMLTestRunner
import sys
reload(sys)
sys.setdefaultencoding("utf-8")


def run_allcase():
    try:
        test_dir = os.path.join(os.getcwd(), "TestCase")
        rep_dir = os.path.join(os.getcwd(), "report/")
        new_time = time.strftime("Report%Y-%m-%d.html", time.localtime())
        rep_name = rep_dir + new_time
        file_open = open(rep_name, "wb")
        discover_test = unittest.defaultTestLoader.discover(
            test_dir, pattern="test_*.py"
        )
        runner = HTMLTestRunner.HTMLTestRunner(
            stream=file_open, title="Test report", description="用例执行情况："
        )
        runner.run(discover_test)
        file_open.close()
    except Exception as e:
        print "running tesecase fail:", e


if __name__ == "__main__":
    run_allcase()

运行单个测试文件是成功的（我把路径打印出来是：/Users/imac/Desktop/Interface/datas/TestData.yaml），加入批量执行用例的时候报错提示找不到 yaml 文件，从报错的信息看少了一层 Interface 文件 (我把路径写成绝对路径批量执行是没有问题)，包括我把相对路径转换成绝对路径都还是报错。。请问下各位该如何解决呢
IOError: [Errno 2] No such file or directory: '/Users/imac/Desktop/datas/TestData.yaml'