Remove testrepository

This commit is a follow-up of "switch to using stestr"
which was merged already [1].
After switch to using stestr, testrepository is unnecessary
and should be removed.

[1] https://review.openstack.org/571969

Change-Id: Ica36bc281afe26c36aedff78c04124261e0afcf3

.gitignore

@@ -31,7 +31,6 @@ pip-log.txt
 .coverage
 .tox
 nosetests.xml
-.testrepository
 .stestr
 .venv
 cover

lower-constraints.txt

@@ -80,7 +80,6 @@ Sphinx==1.6.5
 sphinxcontrib-websupport==1.0.1
 stestr==1.0.0
 stevedore==1.28.0
-testrepository==0.0.18
 testscenarios==0.4
 testtools==2.2.0
 traceback2==1.4.0

test-requirements.txt

@@ -8,7 +8,6 @@ python-cinderclient>=3.3.0 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0
 ddt>=1.0.1 # MIT
 oslotest>=3.2.0 # Apache-2.0
-testrepository>=0.0.18 # Apache-2.0/BSD
 testscenarios>=0.4 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT
 stestr>=1.0.0 # Apache-2.0