Avoid weird test error when mox is missing
Avoid weird test error when mox is missing

Fail early if you can't import mox, rather than return
a cryptic and undecipherable error. Fixes bug 810424.

Change-Id: Ie56d3e7447bbba841fdc882cb1f8f70e234812ef

jianghuaw/nova,hanlind/nova,angdraug/nova,imsplitbit/nova,angdraug/nova,Francis-Liu/animated-broccoli,paulmathews/nova,citrix-openstack-build/nova,tangfeixiong/nova,DirectXMan12/nova-hacking,ted-gould/nova,psiwczak/openstack,jianghuaw/nova,belmiromoreira/nova,akash1808/nova_test_latest,apporc/nova,devendermishrajio/nova,vladikr/nova_drafts,CCI-MOC/nova,nikesh-mahalka/nova,nikesh-mahalka/nova,zaina/nova,petrutlucian94/nova_dev,LoHChina/nova,OpenAcademy-OpenStack/nova-scheduler,Yuriy-Leonov/nova,orbitfp7/nova,JioCloud/nova,mahak/nova,CloudServer/nova,ewindisch/nova,j-carpentier/nova,iuliat/nova,dstroppa/openstack-smartos-nova-grizzly,rrader/nova-docker-plugin,eharney/nova,affo/nova,alaski/nova,JianyuWang/nova,tanglei528/nova,cernops/nova,ruslanloman/nova,maheshp/novatest,eonpatapon/nova,blueboxgroup/nova,joker946/nova,openstack/nova,klmitch/nova,savi-dev/nova,akash1808/nova,dstroppa/openstack-smartos-nova-grizzly,dims/nova,takeshineshiro/nova,eneabio/nova,j-carpentier/nova,eharney/nova,hanlind/nova,houshengbo/nova_vmware_compute_driver,rahulunair/nova,JioCloud/nova,shootstar/novatest,thomasem/nova,TieWei/nova,Juniper/nova,spring-week-topos/nova-week,NeCTAR-RC/nova,gspilio/nova,imsplitbit/nova,JioCloud/nova_test_latest,scripnichenko/nova,cyx1231st/nova,sridevikoushik31/openstack,rickerc/nova_audit,eayunstack/nova,shahar-stratoscale/nova,vmturbo/nova,ruslanloman/nova,usc-isi/nova,mikalstill/nova,watonyweng/nova,mikalstill/nova,sebrandon1/nova,thomasem/nova,barnsnake351/nova,maoy/zknova,ted-gould/nova,dstroppa/openstack-smartos-nova-grizzly,aristanetworks/arista-ovs-nova,plumgrid/plumgrid-nova,yrobla/nova,jianghuaw/nova,NewpTone/stacklab-nova,belmiromoreira/nova,raildo/nova,sacharya/nova,mahak/nova,sridevikoushik31/nova,houshengbo/nova_vmware_compute_driver,klmitch/nova,tealover/nova,redhat-openstack/nova,petrutlucian94/nova,rajalokan/nova,ntt-sic/nova,sridevikoushik31/nova,MountainWei/nova,edulramirez/nova,usc-isi/extra-specs,gooddata/openstack-nova,cernops/nova,felixma/nova,apporc/nova,petrutlucian94/nova,fajoy/nova,leilihh/nova,DirectXMan12/nova-hacking,luogangyi/bcec-nova,alaski/nova,mgagne/nova,tianweizhang/nova,BeyondTheClouds/nova,eonpatapon/nova,devoid/nova,shail2810/nova,maheshp/novatest,cloudbau/nova,josephsuh/extra-specs,projectcalico/calico-nova,sacharya/nova,josephsuh/extra-specs,cloudbau/nova,rrader/nova-docker-plugin,MountainWei/nova,rahulunair/nova,rajalokan/nova,leilihh/nova,shail2810/nova,bigswitch/nova,double12gzh/nova,maheshp/novatest,noironetworks/nova,double12gzh/nova,Brocade-OpenSource/OpenStack-DNRM-Nova,cernops/nova,aristanetworks/arista-ovs-nova,saleemjaveds/https-github.com-openstack-nova,paulmathews/nova,CiscoSystems/nova,psiwczak/openstack,spring-week-topos/nova-week,isyippee/nova,dims/nova,rajalokan/nova,ewindisch/nova,TwinkleChawla/nova,JioCloud/nova_test_latest,Tehsmash/nova,CCI-MOC/nova,takeshineshiro/nova,mandeepdhami/nova,eayunstack/nova,Yusuke1987/openstack_template,Triv90/Nova,cloudbase/nova,usc-isi/nova,badock/nova,alvarolopez/nova,SUSE-Cloud/nova,aristanetworks/arista-ovs-nova,BeyondTheClouds/nova,plumgrid/plumgrid-nova,yosshy/nova,mikalstill/nova,russellb/nova,sebrandon1/nova,isyippee/nova,Stavitsky/nova,cloudbase/nova-virtualbox,leilihh/novaha,SUSE-Cloud/nova,Metaswitch/calico-nova,vladikr/nova_drafts,yosshy/nova,mgagne/nova,mandeepdhami/nova,yatinkumbhare/openstack-nova,viggates/nova,cyx1231st/nova,CloudServer/nova,yrobla/nova,maelnor/nova,OpenAcademy-OpenStack/nova-scheduler,varunarya10/nova_test_latest,NewpTone/stacklab-nova,luogangyi/bcec-nova,LoHChina/nova,alexandrucoman/vbox-nova-driver,tudorvio/nova,bgxavier/nova,barnsnake351/nova,JianyuWang/nova,adelina-t/nova,shahar-stratoscale/nova,tanglei528/nova,zaina/nova,sileht/deb-openstack-nova,blueboxgroup/nova,Tehsmash/nova,psiwczak/openstack,yrobla/nova,kimjaejoong/nova,maelnor/nova,usc-isi/extra-specs,berrange/nova,cloudbase/nova,zzicewind/nova,TwinkleChawla/nova,NoBodyCam/TftpPxeBootBareMetal,sridevikoushik31/openstack,sridevikoushik31/nova,russellb/nova,silenceli/nova,jianghuaw/nova,gooddata/openstack-nova,dawnpower/nova,vmturbo/nova,tealover/nova,mmnelemane/nova,varunarya10/nova_test_latest,virtualopensystems/nova,adelina-t/nova,sileht/deb-openstack-nova,phenoxim/nova,sileht/deb-openstack-nova,joker946/nova,CEG-FYP-OpenStack/scheduler,eneabio/nova,hanlind/nova,cloudbase/nova,redhat-openstack/nova,openstack/nova,gooddata/openstack-nova,alvarolopez/nova,BeyondTheClouds/nova,ntt-sic/nova,Stavitsky/nova,Francis-Liu/animated-broccoli,NoBodyCam/TftpPxeBootBareMetal,mahak/nova,zzicewind/nova,bclau/nova,Triv90/Nova,tudorvio/nova,gspilio/nova,sridevikoushik31/nova,jeffrey4l/nova,usc-isi/extra-specs,russellb/nova,badock/nova,fajoy/nova,devendermishrajio/nova,shootstar/novatest,devendermishrajio/nova_test_latest,TieWei/nova,viggates/nova,houshengbo/nova_vmware_compute_driver,projectcalico/calico-nova,cloudbase/nova-virtualbox,akash1808/nova,alexandrucoman/vbox-nova-driver,jeffrey4l/nova,zhimin711/nova,fnordahl/nova,bigswitch/n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