Tried installing it as root using the form:
zenpack --install=Zenpacks.zenoss.HttpMonitor-2.1.0-py2.7.egg/ZenPacks/zenoss/HttpMonitor/
and seem to get a slightly better error:
zen.AddToPack: Loaded 10 objects into the ZODB database
.....
AttributeError: 'module' object has no attribute '__file__'
Seems likek at least it gets to the ZODB, but is still not finishing cleanly..