使用Twisted子流程和virtualenvwrapper时如何导入模块？

我试图用Twisted编写一个Web服务器，该服务器需要用户输入并根据输入绘制图像。

对于服务器，我有一个简单的Twisted Web服务器。为了处理图像绘图，我使用python wand。我正在安装Twisted和Wand的virtualenvwrapper中工作。但是，当我运行服务器时，出现导入错误：

Traceback (most recent call last):
  File "insert_bubble.py", line 1, in <module>
    from wand.image import Image
ImportError: No module named wand.image

如果我去python解释器，我可以import twisted并且import wand.image很好。我怀疑子流程未使用正确的环境。一种解决方法是将子进程使用的所有模块安装到我的用户帐户，但是我想避免这种情况。

服务器代码主要来自Twisted教程页面。

import sys
from twisted.internet import protocol
from twisted.internet import reactor
import re

class MyPP(protocol.ProcessProtocol):
    def __init__(self, verses):
        self.verses = verses
        self.data = ""
    def connectionMade(self):
        print "connectionMade!"
        self.transport.closeStdin() # tell them we're done
    def outReceived(self, data):
        print "outReceived! with %d bytes!" % len(data)
        self.data = self.data + data
    def errReceived(self, data):
        print "errReceived! with %d bytes!" % len(data)
        self.data= self.data+data
    def inConnectionLost(self):
        print "inConnectionLost! stdin is closed! (we probably did it)"
    def outConnectionLost(self):
        print "outConnectionLost! The child closed their stdout!"
        # now is the time to examine what they wrote
        print "I saw them write:", self.data
        #(dummy, lines, words, chars, file) = re.split(r'\s+', self.data)
        #print "I saw %s lines" % lines
    def errConnectionLost(self):
        print "errConnectionLost! The child closed their stderr."
    def processExited(self, reason):
        print "processExited, status %d" % (reason.value.exitCode,)
    def processEnded(self, reason):
        print "processEnded, status %d" % (reason.value.exitCode,)
        print "quitting"
        reactor.stop()

pp = MyPP(10)
reactor.spawnProcess(pp, sys.executable, ['python', 'insert_bubble.py'], {})
reactor.run()

如何获得子进程以使用正确的virtualenv Python安装，而不是我的家庭环境？