python之"import site' 失败；使用 -v 进行回溯”- mac os lion，python 2.7，子进程

我正在尝试在 python 中运行一个子进程，这是我的代码的一部分:

def update(self): 
        currentTime = strftime("%d.%m.%y %H:%M", gmtime()) #strftime("%d-%m-%y %H:%M", gmtime) 
        resultString = "======== " + currentTime + " ========\n\n"   
        bzrMergeCommand = "cd %s ; /usr/local/bin/bzr merge" % self._directoryName 
        print "Getting the updated code from bzr..." 
        mergeResult = sp.Popen(bzrMergeCommand, shell=True, stdout=sp.PIPE, stderr=sp.PIPE, cwd= self._directoryName) 
 
        communicated = mergeResult.communicate() 

但它无法运行，这是我遇到的异常:

 'import site' failed; use -v for traceback Traceback (most recent call 
 last):   File "/usr/local/bin/bzr", line 21, in <module> 
     import os   File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/os.py", 
 line 398, in <module> 
     import UserDict   File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/UserDict.py", 
 line 84, in <module> 
     _abcoll.MutableMapping.register(IterableUserDict)   File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/abc.py", 
 line 109, in register 
     if issubclass(subclass, cls):   File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/abc.py", 
 line 151, in __subclasscheck__ 
     if subclass in cls._abc_cache:   File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_weakrefset.py", 
 line 69, in __contains__ 
     return ref(item) in self.data TypeError: cannot create weak reference to 'classobj' object 

我在谷歌上搜索并阅读了很多关于“TypeError: cannot create weak reference to 'classobj' object”的内容: https://stackoverflow.com/questions/7753181/making-my-python-script-executable-causes-a-import-site-failed-use-v-for-tra

这里:https://github.com/pypa/virtualenv/issues/108

有什么想法吗？

请您参考如下方法:

出现的错误来自 bzr，而不是您的脚本。尝试运行 python 并输入 import site 如果失败，则您的 python 安装可能有问题。

此外，作为一般规则，除非您有理由在 Popen 中设置 shell=True，否则最好设置 shell=False。