[ussuri][goal] Drop python 2.7 support and testing

OpenStack is dropping the py2.7 support in ussuri cycle.

hacking is ready with python 3 and ok to drop the
python 2.7 support.

Complete discussion & schedule can be found in
- http://lists.openstack.org/pipermail/openstack-discuss/2019-October/010142.html
- https://etherpad.openstack.org/p/drop-python2-support

Ussuri Communtiy-wide goal:
https://governance.openstack.org/tc/goals/selected/ussuri/drop-py27.html

Change-Id: I3ae88a4a11f3c552061eaeb7330d01c1f214bcc6

.zuul.yaml

@@ -3,8 +3,8 @@
       - publish-openstack-docs-pti
       - openstack-cover-jobs
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
+      - openstack-python35-jobs
-      - openstack-python3-train-jobs
+      - openstack-python3-ussuri-jobs
       - openstack-pypy-jobs-nonvoting
       - release-notes-jobs-python3
     check:

doc/requirements.txt

@@ -1,4 +1,3 @@
-sphinx>=1.8.0,<2.0.0;python_version=='2.7' # BSD
+sphinx>=1.8.0,!=2.1.0 # BSD
-sphinx>=1.8.0,!=2.1.0;python_version>='3.4' # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0
 reno>=2.5.0 # Apache-2.0

releasenotes/notes/drop-py-2-7-c2bcdd28e4513532.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. Last release of hacking
+    to support py2.7 is OpenStack Train. The minimum version of Python now
+    supported by hacking is Python 3.5.

setup.cfg

@@ -6,6 +6,7 @@ summary = OpenStack Hacking Guideline Enforcement
 description-file =
     README.rst
 home-page = https://docs.openstack.org/hacking/latest/
+python-requires = >=3.5
 classifier =
     Development Status :: 4 - Beta
     Environment :: Console
@@ -15,9 +16,8 @@ classifier =
     License :: OSI Approved :: Apache Software License
     Operating System :: OS Independent
     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
 

tox.ini

@@ -1,9 +1,11 @@
 [tox]
-minversion = 2.0
+minversion = 3.1.1
 skipsdist = True
-envlist = py27,py36,py37,pep8,pypy
+envlist = py36,py37,pep8,pypy
+ignore_basepython_conflict = True
 
 [testenv]
+basepython = python3
 usedevelop = True
 install_command = pip install {opts} {packages}
 deps =
@@ -14,13 +16,11 @@ commands =
   stestr run --slowest {posargs}
 
 [testenv:integration]
-basepython = python3
 whitelist_externals = bash
 commands =
   bash integration-test/test.sh {posargs}
 
 [testenv:cover]
-basepython = python3
 setenv =
   PYTHON=coverage run --source hacking --parallel-mode
 commands =
@@ -30,7 +30,6 @@ commands =
   coverage xml -o cover/coverage.xml
 
 [testenv:docs]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
   -r{toxinidir}/doc/requirements.txt
@@ -38,18 +37,15 @@ commands =
   sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:releasenotes]
-basepython = python3
 deps =
   {[testenv:docs]deps}
 commands =
   sphinx-build -W -b html releasenotes/source releasenotes/build/html
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:pep8]
-basepython = python3
 commands = flake8 {posargs}
 
 [flake8]
@@ -61,7 +57,6 @@ enable-extensions = H106
 local-check = hacking.tests.test_local.check
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt