Drop python 2.7 support and testing

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

Bifrost 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://review.opendev.org/#/c/691178/

Change-Id: Ia175fc588f283e33efe2961f006c35c4ecc255b1

doc/requirements.txt

@@ -1,5 +1,4 @@
-sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7' # BSD
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2;python_version>='3.4' # BSD
+sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
 sphinxcontrib-httpdomain>=1.3.0 # BSD
 sphinxcontrib-blockdiag>=1.5.4 # BSD
 sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD

releasenotes/notes/drop-python2-f465181d67cccd30.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. Last release of bifrost
+    to support Python 2.7 is OpenStack Train. The minimum version
+    of Python now supported by bifrost is Python 3.6.

setup.cfg

@@ -13,8 +13,6 @@ 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 :: 3.6
     Programming Language :: Python :: 3.7

tox.ini

@@ -1,12 +1,13 @@
 [tox]
 minversion = 3.1.0
-envlist = py3,py27,docs,pep8
+envlist = py3,docs,pep8
 skipsdist = True
 ignore_basepython_conflict=true
 
 [testenv]
 usedevelop = True
 install_command = pip install -U -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master} {opts} {packages}
+basepython = python3
 setenv =
    VIRTUAL_ENV={envdir}
    PYTHONWARNINGS=default::DeprecationWarning
@@ -16,23 +17,19 @@ commands = python setup.py test --slowest --testr-args='{posargs}'
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 
 [testenv:pep8]
-basepython = python3
 commands = flake8
            doc8 doc/source releasenotes/source README.rst CONTRIBUTING.rst MISSION.rst HACKING.rst
 
 [testenv:venv]
-basepython = python3
 deps =
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/doc/requirements.txt
 commands = {posargs}
 
 [testenv:cover]
-basepython = python3
 commands = python setup.py test --coverage --testr-args='{posargs}'
 
 [testenv:docs]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/requirements.txt
@@ -40,27 +37,20 @@ deps =
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:pdf-docs]
-basepython = python3
 whitelist_externals = make
 deps = {[testenv:docs]deps}
 commands = sphinx-build -W -b latex doc/source doc/build/pdf
            make -C doc/build/pdf
 
 [testenv:debug]
-basepython = python3
 commands = oslo_debug_helper -t bifrost/tests {posargs}
 
 [testenv:releasenotes]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
-[testenv:debug-py27]
-basepython = python2.7
-commands = oslo_debug_helper -t bifrost/tests {posargs}
-
 [testenv:debug-py36]
 basepython = python3.6
 commands = oslo_debug_helper -t bifrost/tests {posargs}
@@ -71,7 +61,6 @@ ignore = F403,H102,H303
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build,os_ironic.py,os_ironic_node.py,os_ironic_inspect.py,os_keystone_service.py
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt