Get rid of Python 2 support

2020 is coming, everyone should be using Python 3 now.

As per the official python support timeline set forth by the OpenStack
TC [1], OpenStack Train (in our case, kolla-ansible 9.x) is the last
release that will support python2.7.

[1] https://governance.openstack.org/tc/resolutions/20180529-python2-deprecation-timeline.html

Implements: blueprint drop-py2-support

Change-Id: Ibb3b12a779ecfd424053d0b3e98dac2f21d909bc

bindep.txt

@@ -3,8 +3,6 @@ libffi-dev [platform:dpkg]
 libffi-devel [platform:rpm]
 gcc [platform:rpm]
 gcc [platform:dpkg]
-python-dev [platform:dpkg]
-python-devel [platform:rpm]
 python3-dev [platform:dpkg]
 python3-devel [platform:rpm]
 openssl-devel [platform:rpm]

doc/requirements.txt

@@ -7,6 +7,5 @@
 # be installed in a specific order.
 openstackdocstheme>=1.19.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
-sphinx>=1.8.0,<2.0.0;python_version=='2.7' # BSD
 sphinx>=1.8.0,!=2.1.0;python_version>='3.4'  # BSD
 sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD

releasenotes/notes/drop-py27-509835da35f047b4.yaml

+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. Last release of kolla-ansible to
+    support Python 2.7 is OpenStack Train. The minimum version of Python now
+    supported by kolla-ansible is Python 3.6.

setup.cfg

@@ -14,8 +14,6 @@ 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

 [tox]
 minversion = 2.5.0
 skipsdist = True
-envlist = py27,py37,pep8,pypy
+envlist = py37,pep8,pypy
 
 [testenv]
+basepython = python3
 usedevelop=True
 whitelist_externals = find
                       rm
@@ -20,11 +21,9 @@ commands =
   stestr run --slowest {posargs}
 
 [testenv:debug]
-basepython = python3
 commands = oslo_debug_helper -t tests {posargs}
 
 [testenv:cover]
-basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          NOSE_WITH_COVERAGE=1
          NOSE_COVER_BRANCHES=1
@@ -38,7 +37,6 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:pep8]
-basepython = python3
 # sphinx needs to be installed to make doc8 work properly
 deps =
     {[testenv]deps}
@@ -54,11 +52,9 @@ commands =
 
 [testenv:bandit]
 # B303: Use of insecure MD2, MD4, MD5, or SHA1 hash function.
-basepython = python3
 commands = bandit --skip B303 -r ansible kolla_ansible tests tools
 
 [testenv:venv]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/test-requirements.txt
@@ -66,7 +62,6 @@ deps =
 commands = {posargs}
 
 [testenv:docs]
-basepython = python3
 deps =
    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
    -r{toxinidir}/requirements.txt
@@ -76,7 +71,6 @@ commands =
   sphinx-build -W --keep-going -b html doc/source doc/build/html
 
 [testenv:deploy-guide]
-basepython = python3
 deps =
    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
    -r{toxinidir}/requirements.txt
@@ -87,7 +81,6 @@ commands =
   sphinx-build -a -E -W -d deploy-guide/build/doctrees --keep-going -b html deploy-guide/source deploy-guide/build/html
 
 [testenv:pdf-docs]
-basepython = python3
 whitelist_externals = make
 deps = {[testenv:docs]deps}
 commands =
@@ -95,7 +88,6 @@ commands =
   make -C doc/build/pdf
 
 [testenv:releasenotes]
-basepython = python3
 deps =
    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
    -r{toxinidir}/requirements.txt
@@ -109,7 +101,6 @@ show-source = True
 exclude=.eggs,.git,.tox,doc
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt