Remove python2 jobs for tap-as-a-service

Since neutron-lib changed to python3 only (see [0]) it's time to remove
python2 jobs for tap-as-a-service.

[0]: https://review.opendev.org/702098

Change-Id: I4a8b016377805d6f304c08baee2ef7e161697112

.zuul.yaml

@@ -1,6 +1,9 @@
 - project:
     templates:
       - openstack-lower-constraints-jobs
+      - openstack-cover-jobs-neutron
+      - check-requirements
+      - openstack-python3-ussuri-jobs-neutron
       - tap-as-a-service-tempest-plugin-jobs
     check:
       jobs:

setup.cfg

@@ -13,10 +13,10 @@ classifier =
     License :: OSI Approved :: Apache Software License
     Operating System :: POSIX :: Linux
     Programming Language :: Python
-    Programming Language :: Python :: 2
-    Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.5
+    Programming Language :: Python :: 3.6
+    Programming Language :: Python :: 3.7
 
 [files]
 packages =

tox.ini

@@ -4,6 +4,7 @@ minversion = 1.8
 skipsdist = True
 
 [testenv]
+basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          PYTHONWARNINGS=default::DeprecationWarning
 usedevelop = True
@@ -32,7 +33,6 @@ commands =
 commands = {posargs}
 
 [testenv:cover]
-basepython = python2.7
 setenv =
   {[testenv]setenv}
   PYTHON=coverage run --source neutron_taas --parallel-mode
@@ -64,7 +64,6 @@ exclude=.venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build
 import_exceptions = neutron_taas._i18n
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt
@@ -77,7 +76,6 @@ commands =
     pip install -q -e "git+https://opendev.org/openstack/neutron#egg=neutron"
 
 [testenv:py3-dev]
-basepython = python3
 commands =
     {[testenv:dev]commands}
     {[testenv]commands}