Drop python 2.7 support and testing

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

ironic-prometheus-exporter 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: I0a85f50fa3b0066e642cabf640ca8fed1c65f1a0

.zuul.yaml

@@ -1,6 +1,5 @@
 - project:
     templates:
       - check-requirements
-      - openstack-python-jobs
       - openstack-python3-ussuri-jobs
       - release-notes-jobs-python3

doc/requirements.txt

@@ -1,4 +1,3 @@
 openstackdocstheme>=1.20.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
-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

releasenotes/notes/drop-py-2-7-e49209f779b36a1c.yaml

@@ -0,0 +1,7 @@
+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. Last release of
+    ironic-prometheus-exporter to support Python 2.7 is OpenStack Train.
+    The minimum version of Python now supported by ironic-prometheus-exporter
+    is Python 3.6.

setup.cfg

@@ -14,8 +14,6 @@ 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 :: 3.6
     Programming Language :: Python :: 3.7

tox.ini

@@ -1,9 +1,10 @@
 [tox]
 minversion = 2.0
-envlist = py3,py27,pep8
+envlist = py3,pep8
 skipsdist = True
 
 [testenv]
+basepython = python3
 usedevelop = True
 install_command = pip install {opts} {packages}
 setenv =
@@ -19,11 +20,9 @@ deps  =
 commands = stestr run {posargs}
 
 [testenv:pep8]
-basepython = python3
 commands = flake8 {posargs}
 
 [testenv:releasenotes]
-basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
@@ -31,11 +30,12 @@ commands =
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:venv]
-basepython = python3
 setenv = PYTHONHASHSEED=0
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/doc/requirements.txt
 commands = {posargs}
 
 [flake8]