greenplum源码安装，在gpinitsystem时报错缺少相关python包

greenplum源码安装，在gpinitsystem时报错，不断的报python相关的错误，补完一个python包又会出现缺少另外一个包。
报错类似如下：
20151222:13:58:42:014218 gpinitsystem:test:gpadmin-[INFO]:-Starting the Master in admin mode
Traceback (most recent call last):
File "/home/gpadmin/greenplum/bin/lib/gphostcachelookup.py", line 12, in

from gppylib.gphostcache import GpInterfaceToHostNameCache

ImportError: No module named gppylib.gphostcache
20151222:13:58:45:gpinitsystem:test:gpadmin-[FATAL]:-Unknown host Script Exiting!