[ussuri][goal] Drop python 2.7 support and testing

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

designate-tempest-plugin 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://governance.openstack.org/tc/goals/selected/ussuri/drop-py27.html

Change-Id: Ib3bd70ba8f2e8386643c536ac8194fa99b54b842
diff --git a/releasenotes/notes/drop-py-2-7-a36c3b1d4d875e21.yaml b/releasenotes/notes/drop-py-2-7-a36c3b1d4d875e21.yaml
new file mode 100644
index 0000000..c6686ed
--- /dev/null
+++ b/releasenotes/notes/drop-py-2-7-a36c3b1d4d875e21.yaml
@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Python 2.7 support has been dropped. Last release of designate-tempest-plugin
+    to support py2.7 is OpenStack Train. The minimum version of Python now
+    supported by designate-tempest-plugin is Python 3.6.
diff --git a/requirements.txt b/requirements.txt
index 2af96d6..8d0dc5f 100644
--- a/requirements.txt
+++ b/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.
 
-dnspython>=1.14.0;python_version=='2.7' # http://www.dnspython.org/LICENSE
-dnspython3!=1.13.0,!=1.14.0,>=1.12.0;python_version>='3.0' # http://www.dnspython.org/LICENSE
+dnspython3!=1.13.0,!=1.14.0,>=1.12.0 # http://www.dnspython.org/LICENSE
 ddt>=1.0.1 # MIT
 testtools>=2.2.0 # MIT
 tempest>=17.1.0 # Apache-2.0
diff --git a/setup.cfg b/setup.cfg
index 1e21e36..bf0b008 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -14,10 +14,9 @@
     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 :: 3.5
+    Programming Language :: Python :: 3.6
+    Programming Language :: Python :: 3.7
     Topic :: Internet :: Name Service (DNS)
 
 [global]
diff --git a/test-requirements.txt b/test-requirements.txt
index bbf8861..6e6ab00 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -5,5 +5,4 @@
 # Hacking already pins down pep8/pycodestyle pyflakes and flake8
 hacking>=1.1.0,<1.2.0 # Apache-2.0
 openstackdocstheme>=1.18.1 # 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,>=1.6.2;python_version>='3.4'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2  # BSD
diff --git a/tox.ini b/tox.ini
index 7490e90..6211c66 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,9 +1,11 @@
 [tox]
-minversion = 2.0
-envlist = py35,py27,pep8
+minversion = 3.1.1
+envlist = py37,pep8
 skipsdist = True
+ignore_basepython_conflict = True
 
 [testenv]
+basepython = python3
 usedevelop = True
 install_command = pip install {opts} {packages}
 deps =
@@ -31,12 +33,10 @@
           OS_STDOUT_CAPTURE
 
 [testenv:pep8]
-basepython = python3
 commands = sh tools/pretty_flake8.sh
 
 
 [testenv:docs]
-basepython = python3
 commands = rm -rf doc/build
            sphinx-build -E -W -b html doc/source doc/build/html
 
@@ -67,7 +67,6 @@
 commands=pip-missing-reqs -d --ignore-file=designate/tests/* designate
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [flake8]