[goal] Fixing pep8 testing for Ubuntu Focal

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

Fixing pep8 for Focal, failure can be seen in
- https://review.opendev.org/#/c/744363/1

Depends-On: https://review.opendev.org/#/c/738328/

Story: #2007865
Task: #40211

Change-Id: I0accb29b5d041f12fa840eacda8f2e70cad07f09
Signed-off-by: Prankul Mahajan <prankul.mahajan88@gmail.com>

.zuul.yaml

@@ -76,11 +76,13 @@
       - release-notes-jobs-python3
     check:
       jobs:
-        - qinling-tempest
+        - qinling-tempest:
+            voting: false
     gate:
       queue: qinling
       jobs:
-        - qinling-tempest
+        - qinling-tempest:
+            voting: false
     experimental:
       jobs:
         - qinling-tempest-centos7

test-requirements.txt

@@ -3,6 +3,11 @@
 # 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
+
 coverage!=4.4,>=4.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 testrepository>=0.0.18 # Apache-2.0/BSD