[goal] Migrate testing to ubuntu focal

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

Bump the pyflakes to 2.1.1 as min version to run pep8 jobs
on py3.8 which is default python vesion in ubuntu focal.

Bump cassandra-driver to 3.21.0 in lower-constraints.txt
since it is the min version with py3.8 support [2]

Bump kazoo to 2.8.0 in lower-constraints.txt
since it is the min version with py3.8 support [3]

Story: #2007865
Task: #40197

[1] https://governance.openstack.org/tc/goals/selected/victoria/migrate-ci-cd-jobs-to-ubuntu-focal.html
[2] https://pypi.org/project/cassandra-driver/3.21.0/
[3] python-zk/kazoo@6b6ffe6

Change-Id: I3a465aa0b26dd72432696d2dd19c955eb3e974e5

lower-constraints.txt

@@ -1,7 +1,7 @@
 appdirs==1.3.0
 Babel==2.3.4
 bandit==1.4.0
-cassandra-driver==3.11.0
+cassandra-driver==3.21.0
 coverage==4.0
 debtcollector==1.2.0
 docutils==0.11
@@ -15,7 +15,7 @@ GitPython==1.0.1
 greenlet==0.4.10
 influxdb==2.9.2
 iso8601==0.1.11
-kazoo==2.2
+kazoo==2.8.0
 keystoneauth1==3.4.0
 linecache2==1.0.0
 mccabe==0.4.0

requirements.txt

@@ -6,5 +6,5 @@ oslo.log>=3.36.0 # Apache-2.0
 
 six>=1.10.0 # MIT
 monasca-common>=2.16.0 # Apache-2.0
-cassandra-driver>=3.11.0
+cassandra-driver>=3.21.0
 simplejson>=3.8.1

setup.cfg

@@ -38,7 +38,7 @@ data_files =
 influxdb =
   influxdb>=2.9.2 # MIT
 cassandra =
-  cassandra-driver>=3.11.0 # Apache-2.0
+  cassandra-driver>=3.21.0 # Apache-2.0
 elasticsearch =
   elasticsearch<3.0.0,>=2.0.0 # Apache-2.0
 

test-requirements.txt

@@ -4,12 +4,16 @@
 bandit>=1.1.0 # Apache-2.0
 flake8<2.6.0,>=2.5.4 # MIT
 hacking>=3.0.1,<3.1.0 # 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
 stestr>=1.0.0 # Apache-2.0
 docutils>=0.11 # OSI-Approved Open Source, Public Domain
 pycodestyle>=2.5.0 # MIT
-cassandra-driver>=3.11.0
+cassandra-driver>=3.21.0
 
 # release notes
 sphinx>=2.0.0,!=2.1.0 # BSD