我已经以常规方式安装了 pyxb 模块（python setup.py install），这是输出：
Found bundle in pyxb/bundles/common
Found bundle in pyxb/bundles/dc
Found bundle in pyxb/bundles/wssplat
Found bundle in pyxb/bundles/saml20
running install
running build
running build_py
running build_scripts
running install_lib
running install_scripts
changing mode of /usr/local/bin/pyxbgen to 755
changing mode of /usr/local/bin/pyxbwsdl to 755
changing mode of /usr/local/bin/pyxbdump to 755
running install_egg_info
Removing /usr/local/lib/python2.7/dist-packages/PyXB-1.2.4.egg-info
Writing /usr/local/lib/python2.7/dist-packages/PyXB-1.2.4.egg-info
但是，我不断收到消息：
ImportError: No module named pyxb
运行包含以下内容的脚本时：
import pyxb
import pyxb.binding
import pyxb.binding.saxer
import StringIO
import pyxb.utils.utility
import pyxb.utils.domutils
有谁知道为什么会发生这种情况？