i am installing devstack on ubuntu 16 machine

i got following error using devstack

1773 static files copied to '/opt/stack/horizon/static'.
+lib/horizon:init_horizon:154              DJANGO_SETTINGS_MODULE=openstack_dashboard.settings
+lib/horizon:init_horizon:154              django-admin compress --force
Found 'compress' tags in:
        /opt/stack/horizon/openstack_dashboard/templates/horizon/_scripts.html
        /opt/stack/horizon/openstack_dashboard/templates/horizon/_conf.html
        /opt/stack/horizon/openstack_dashboard/templates/_stylesheets.html
Compressing... CommandError: An error occurred during rendering /opt/stack/horizon/openstack_dashboard/templates/_stylesheets.html: Couldn't find anything to import: /app/core/cluster.scss
Extensions: <NamespaceAdapterExtension>, <DjangoExtension>, <CompassExtension>
Search path:

on line 1 of u'string:299652627aecc518:\n    // My Themes\n@import "/themes/default/variables";\n\n// Horizon\n@import "/dashboard/scss/horizon.'
+lib/horizon:init_horizon:1                exit_trap
+./stack.sh:exit_trap:487                  local r=1
++./stack.sh:exit_trap:488                  jobs -p
+./stack.sh:exit_trap:488                  jobs=
+./stack.sh:exit_trap:491                  [[ -n '' ]]
+./stack.sh:exit_trap:497                  kill_spinner
+./stack.sh:kill_spinner:383               '[' '!' -z '' ']'
+./stack.sh:exit_trap:499                  [[ 1 -ne 0 ]]
+./stack.sh:exit_trap:500                  echo 'Error on exit'
Error on exit
+./stack.sh:exit_trap:501                  generate-subunit 1486466237 1730 fail
+./stack.sh:exit_trap:502                  [[ -z /opt/stack/logs ]]
+./stack.sh:exit_trap:505                  /home/stack/devstack/tools/worlddump.py -d /opt/stack/logs
World dumping... see /opt/stack/logs/worlddump-2017-02-07-114607.txt for details
+./stack.sh:exit_trap:511                  exit 1

please help me

thanks sagar