Drop python 2.7 support and testing

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

Change-Id: I94e709093e01825069b44b6c485e49a81f8f14c1
Sem-Ver: api-break

.zuul.yaml

@@ -1,11 +1,9 @@
 - project:
     templates:
       - check-requirements
-      - lib-forward-testing
       - lib-forward-testing-python3
       - openstack-cover-jobs
       - openstack-lower-constraints-jobs
-      - openstack-python-jobs
       - openstack-python3-ussuri-jobs
       - periodic-stable-jobs
       - publish-openstack-docs-pti

doc/requirements.txt

@@ -2,8 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 # this is required for the docs build jobs
-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
 openstackdocstheme>=1.20.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD

releasenotes/notes/drop-python27-support-7d837a45dae941bb.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Python 2.7 is no longer supported. The minimum supported version of Python
+    is now Python 3.6.

requirements.txt

@@ -3,7 +3,6 @@
 # process, which may cause wedges in the gate later.
 
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
-enum34>=1.0.4;python_version=='2.7' or python_version=='2.6' or python_version=='3.3' # BSD
 oslo.config>=5.2.0 # Apache-2.0
 oslo.i18n>=3.15.3 # Apache-2.0
 oslo.utils>=3.33.0 # Apache-2.0

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/oslo.concurrency/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -13,11 +14,11 @@ 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 =
@@ -29,15 +30,6 @@ oslo.config.opts =
 console_scripts =
     lockutils-wrapper = oslo_concurrency.lockutils:main
 
-[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_concurrency/locale
 domain = oslo_concurrency
@@ -52,8 +44,5 @@ keywords = _ gettext ngettext l_ lazy_gettext
 mapping_file = babel.cfg
 output_file = oslo_concurrency/locale/oslo_concurrency.pot
 
-[pbr]
-warnerrors = True
-
 [bdist_wheel]
 universal = 1

test-requirements.txt

@@ -5,10 +5,8 @@
 hacking>=1.1.0,<1.2.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0
-futures>=3.0.0;python_version=='2.7' or python_version=='2.6' # BSD
 fixtures>=3.0.0 # Apache-2.0/BSD
 stestr>=2.0.0 # Apache-2.0
-
 eventlet!=0.18.3,!=0.20.1,>=0.18.2 # MIT
 
 # Bandit security code scanner

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 3.1
-envlist = py27,py37,pep8
+envlist = py37,pep8
 ignore_basepython_conflict = True
 
 [testenv]