尝试在Python中导入Prov模块时出现ImportError

尝试从Prov包导入模块时收到此错误。这是我文件的内容：

#!/usr/bin/env
import sys
egg_path='/Library/Python/2.7/site-packages/prov-1.5.0-py2.7.egg/prov'
sys.path.append(egg_path)
#... rest of code
import model as prov

def main():
    # Create a new provenance document
    d1 = ProvDocument()  # d1 is now an empty provenance document
    # Declaring namespaces for various prefixes used in the example
    d1.add_namespace('now', 'http://www.provbook.org/nownews/')
    d1.add_namespace('nowpeople', 'http://www.provbook.org/nownews/people/')
    d1.add_namespace('bk', 'http://www.provbook.org/ns/#')

    # Entity: now:employment-article-v1.html
    e1 = d1.entity('now:employment-article-v1.html')
    # Agent: nowpeople:Bob
    d1.agent('nowpeople:Bob')

这是输出：

Traceback (most recent call last): File "prov.py", line 6, in <module> import model as prov File "/Library/Python/2.7/site-packages/prov-1.5.0-py2.7.egg/prov/model.py", line 25, in <module> from prov import Error, serializers ImportError: cannot import name Error

有什么想法或解决办法吗？我使用easy_install prov安装了Prov。