Switch ostestr to 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: Ic580dc7ba0684087a81137771fb125f4d412d948
Signed-off-by: Charles Short <zulcss@gmail.com>

.stestr.conf

@@ -1,3 +1,3 @@
 [DEFAULT]
-test_path=./sahara/tests
+test_path=./sahara/tests/unit
 top_dir=./

test-requirements.txt

@@ -12,7 +12,7 @@ doc8>=0.6.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
 mock>=2.0.0 # BSD
 oslotest>=3.2.0 # Apache-2.0
-os-testr>=1.0.0 # Apache-2.0
+stestr>=1.0.0 # Apache-2.0
 psycopg2>=2.6.2 # LGPL/ZPL
 pylint==1.4.5 # GPLv2
 testresources>=2.0.0 # Apache-2.0/BSD

tox.ini

@@ -12,7 +12,7 @@ setenv =
 deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 
 [testenv:cover]