zuul: Remove unnecessary 'USE_PYTHON3'

The DevStack change to switch to Python 3 by default [1] has now landed,
which means we no longer need to override this in our zuul
configuration. Remove the relevant entries.

[1] https://review.opendev.org/#/c/649097/

Change-Id: I40e515cd4ddc85cd1dba613c2b5c0505e35df295
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

.zuul.yaml

@@ -1,10 +1,6 @@
 # See https://docs.openstack.org/infra/manual/drivers.html#naming-with-zuul-v3
 # for job naming conventions.
 
-# TODO(stephenfin): Remove 'USE_PYTHON3' once [1] or similar merges
-#
-# [1] https://review.opendev.org/#/c/649097/
-#
 - job:
     name: nova-dsvm-multinode-base
     parent: legacy-dsvm-base-multinode
@@ -136,7 +132,6 @@
               resize: false
               cold_migration: false
       devstack_localrc:
-        USE_PYTHON3: True
         NOVA_BACKEND: LVM
         # Do not waste time clearing volumes.
         LVM_VOLUME_CLEAR: none
@@ -198,7 +193,6 @@
               bridge_mappings: public:br-ex
               resource_provider_bandwidths: br-ex:1000000:1000000
       devstack_localrc:
-        USE_PYTHON3: True
         # Added in Pike.
         NOVA_USE_SERVICE_TOKEN: True
         # Enable TLS between the noVNC proxy & compute nodes; this requires
@@ -219,7 +213,6 @@
     group-vars:
       subnode:
         devstack_localrc:
-          USE_PYTHON3: True
           NOVA_USE_SERVICE_TOKEN: True
           NOVA_CONSOLE_PROXY_COMPUTE_TLS: True
         devstack_services:
@@ -239,7 +232,6 @@
       tox_envlist: all
       tempest_test_regex: api.*compute
       devstack_localrc:
-        USE_PYTHON3: True
         TEMPEST_COMPUTE_TYPE: compute_legacy
 
 - job:
@@ -299,7 +291,6 @@
         # Disable other non-essential services that we don't need for this job.
         c-bak: false
       devstack_localrc:
-        USE_PYTHON3: True
         # Setup two non-cell0 cells (cell1 and cell2).
         NOVA_NUM_CELLS: 2
         # Resize to the same host is supported for now since we only have
@@ -313,12 +304,10 @@
     group-vars:
       peers:
         devstack_localrc:
-          USE_PYTHON3: True
           NOVA_ALLOW_MOVE_TO_SAME_HOST: true
           LIVE_MIGRATION_AVAILABLE: false
       subnode:
         devstack_localrc:
-          USE_PYTHON3: True
           # The subnode compute will get registered with cell2.
           NOVA_CPU_CELL: 2
         devstack_services:

doc/source/contributor/testing/eventlet-profiling.rst

@@ -79,7 +79,6 @@ profiling and benchmarking scenarios so not all changes are relevant here):
     DATABASE_PASSWORD=$ADMIN_PASSWORD
     RABBIT_PASSWORD=$ADMIN_PASSWORD
     SERVICE_PASSWORD=$ADMIN_PASSWORD
-    USE_PYTHON3=True
     VIRT_DRIVER=fake
     # You may use different numbers of fake computes, but be careful: 100 will
     # completely overwhelm a 16GB, 16VPCU server. In the test profiles below a