Drop python 2.7 support and testing

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

Change-Id: Ie875138bd1b773f460698e1eacc9dab542318e30
Sem-Ver: api-break

.zuul.yaml

@@ -1,10 +1,8 @@
 - project:
     templates:
       - check-requirements
-      - lib-forward-testing
       - lib-forward-testing-python3
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
       - openstack-python3-ussuri-jobs
       - periodic-stable-jobs
       - publish-openstack-docs-pti

doc/requirements.txt

@@ -3,7 +3,6 @@
 # process, which may cause wedges in the gate later.
 # These are needed for docs generation
 openstackdocstheme>=1.20.0 # 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
+sphinx>=1.8.0,!=2.1.0 # BSD
 reno>=2.5.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD

releasenotes/notes/drop-python27-support-b421329839e69d41.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Python 2.7 is no longer supported. The minimum supported version of Python
+    is now Python 3.

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/oslo.context/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -13,25 +14,16 @@ 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
+    Programming Language :: Python :: 3 :: Only
+    Programming Language :: Python :: Implementation :: CPython
 
 [files]
 packages =
     oslo_context
 
-[build_sphinx]
-source-dir = doc/source
-build-dir = doc/build
-all_files = 1
-warning-is-error = 1
-
-[upload_sphinx]
-upload-dir = doc/build/html
-
 [compile_catalog]
 directory = oslo_context/locale
 domain = oslo_context

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 minversion = 3.1
-envlist = py27,py37,pep8
-ignore_basepython_conflict = True
+envlist = py37,pep8
+ignore_basepython_conflict = true
 
 [testenv]
 basepython = python3
@@ -13,6 +13,7 @@ commands = stestr run --slowest {posargs}
 
 [testenv:pep8]
 deps =
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/test-requirements.txt
 commands =
   flake8
@@ -42,8 +43,7 @@ commands =
 
 [flake8]
 # E123, E125 skipped as they are invalid PEP-8.
-
-show-source = True
+show-source = true
 ignore = E123,E125
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build