[goal] Migrate ec2api-tempest-plugin jobs to focal

As per victoria cycle testing runtime and community goal[1]
we need to migrate upstream CI/CD to Ubuntu Focal(20.04).

Most of the Tempest jobs will be migrate automatically once devstack
base job start running on Focal(Depends-On).

Stable jobs testing stable branch needs to keep running on their supported
distro version which is bionic from stein till ussuri.

[1] https://governance.openstack.org/tc/goals/selected/victoria/migrate-ci-cd-jobs-to-ubuntu-focal.html

Change-Id: I4b8747d2ce5f73a467678883bbc71d388ea8f228
Story: #2007865
Task: #40183

.zuul.yaml

@@ -13,14 +13,17 @@
 - job:
     name: ec2-api-functional-neutron-ussuri
     parent: ec2-api-functional-neutron
+    nodeset: openstack-single-node-bionic
     override-checkout: stable/ussuri
 
 - job:
     name: ec2-api-functional-neutron-train
     parent: ec2-api-functional-neutron
+    nodeset: openstack-single-node-bionic
     override-checkout: stable/train
 
 - job:
     name: ec2-api-functional-neutron-stein
     parent: ec2-api-functional-neutron
+    nodeset: openstack-single-node-bionic
     override-checkout: stable/stein     

ec2api_tempest_plugin/base.py

@@ -438,7 +438,7 @@ class EC2TestCase(base.BaseTestCase):
                     obj_id = obj_id(kw_args)
                     try:
                         waiter().wait_delete(obj_id)
-                    except botocore.exceptions.ClientError as e:
+                    except botocore.exceptions.ClientError:
                         LOG.exception('Exception occurred in cleanup waiting')
                         return False
             except botocore.exceptions.ClientError as e:

test-requirements.txt

@@ -3,3 +3,8 @@
 # process, which may cause wedges in the gate later.
 
 hacking<0.13,>=0.12.0 # Apache-2.0
+
+# remove this pyflakes from here once you bump the
+# hacking to 3.2.0 or above. hacking 3.2.0 takes
+# care of pyflakes version compatibilty.
+pyflakes>=2.1.1