Switch to using stestr

According to Openstack summit session [1] stestr is
maintained project to which all Openstack projects
should migrate.
Let's switch it then.

[1] https://etherpad.openstack.org/p/YVR-python-pti

Change-Id: I847368004d14c2f213d36c602398abfdbfa381cd
Signed-off-by: Charles Short <zulcss@gmail.com>

.stestr.conf

@@ -0,0 +1,3 @@
+[DEFAULT]
+test_path=${OS_TEST_PATH:-./designate/tests}
+top_dir=./

test-requirements.txt

@@ -7,7 +7,7 @@ hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
 mock>=2.0.0 # BSD
-os-testr>=1.0.0 # Apache-2.0
+stestr>=2.0.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 requests-mock>=1.2.0 # Apache-2.0
 testtools>=2.2.0 # MIT

tox.ini

@@ -30,12 +30,13 @@ passenv = http_proxy
 [testenv:py27]
 commands =
   {[testenv]commands}
-  sh tools/pretty_tox.sh '{posargs}'
+  stestr run '{posargs}'
+  stestr slowest
 
 [testenv:py35]
 commands =
   {[testenv]commands}
-  ostestr '{posargs}'
+  stestr run '{posargs}'
 
 [testenv:docs]
 deps =