After upgrading a host during a RHEV 3.4 to 3.5 upgrade, it cannot be activated as VDSM fails to start

Issue

• After upgrading a host during a RHEV 3.4 to 3.5 upgrade, the host cannot be activated.

• The vdsmd service fails to restart.

• The messages file on the host contains;

Jun 10 09:25:52 host-A python: module upgrade_300_networks could not load to vdsm-tool: Traceback (most recent call last):#012  File "/usr/bin/vdsm-tool", line 81, in load_modules#012    mod_absp, mod_desc)#012  File "/usr/lib64/python2.6/site-packages/vdsm/tool/upgrade_300_networks.py", line 30, in <module>#012    from netconf import ifcfg#012ImportError: No module named netconf