[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).

Fixing:
- bug#1886298
Bump the lower constraints for required deps which added python3.8
support in their later version.
Story: #2007865
Task: #40197

Closes-Bug: #1886298

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

Change-Id: I88cdf86365a0af8450e5fb823eab830834ce8fa1

lower-constraints.txt

@@ -4,13 +4,13 @@ appdirs==1.3.0
 asn1crypto==0.23.0
 Babel==2.3.4
 cachetools==2.0.0
-cffi==1.7.0
+cffi==1.14
 cliff==2.8.0
 cmd2==0.8.0
 colorama==0.3.9
 contextlib2==0.4.0
-coverage==4.0
-cryptography==2.1
+coverage==5.2.1
+cryptography==3.0
 debtcollector==1.2.0
 decorator==3.4.0
 deprecation==1.0
@@ -27,7 +27,7 @@ fasteners==0.7.0
 fixtures==3.0.0
 funcsigs==1.0.0
 futurist==1.2.0
-greenlet==0.4.10
+greenlet==0.4.15
 horizon==18.3.0
 idna==2.6
 imagesize==0.7.1
@@ -41,7 +41,7 @@ keystoneauth1==3.4.0
 kombu==4.0.0
 linecache2==1.0.0
 MarkupSafe==1.0
-mccabe==0.2.1
+mccabe==0.6.1
 monotonic==0.6
 mox3==0.20.0
 msgpack-python==0.4.0
@@ -77,7 +77,7 @@ pycparser==2.18
 Pygments==2.2.0
 pyinotify==0.9.6
 pymongo==3.0.2
-pyOpenSSL==17.1.0
+pyOpenSSL==19.1.0
 pyparsing==2.1.0
 pyperclip==1.5.27
 pyScss==1.3.7

test-requirements.txt

@@ -4,7 +4,7 @@
 # Hacking already pins down pep8, pyflakes and flake8
 hacking>=3.0.1,<3.1.0 # Apache-2.0
 
-coverage!=4.4,>=4.0 # Apache-2.0
+coverage>=5.2.1 # Apache-2.0
 nodeenv>=0.9.4 # BSD
 selenium>=2.50.1 # Apache-2.0