用objgraph包来绘制引用关系时遇到的错误

ImportError: No module named objgraph

#pip install xdot
#pip install objgraph

AttributeError: ‘module’ object has no attribute ‘F_GETFD’

Image renderer (dot) not found, not doing anything else

xdot是graphviz（http://www.graphviz.org/）的一个命令，安装graphviz即可

#pip install graphviz
或者
#yum install graphviz
恢复正常