tox: Suppress output

Since the switch to stestr in commit 2222dbb47, the tests have taken to
spewing a load of noise. This seems to be because we dropped the
configuration for OS_STDOUT_CAPTURE and OS_STDERR_CAPTURE, which was
previously configured in '.testr.conf'. This is fixed. However, it seems
it's also necessary to explicitly pass the '--suppress-attachments'
option to 'stestr' to properly silence things. This seems to be
necessary because many pbr commands output to stdout by default, while
other projects (nova, etc.) use 'logging'. Use of this option requires
stestr 2.1.0 [1] so we bump the lower-constraint.

As an aside, finding out what caused this output was easier said than
done. I tried stestr, testr and fixtures, before finally finding it in
subunit.

[1] https://github.com/mtreinish/stestr/commit/1316ebd7

Change-Id: I1678bcd26b41fdf09f98c36fc095d6d4c1826deb
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

lower-constraints.txt

@@ -26,7 +26,7 @@ six==1.10.0
 snowballstemmer==1.2.1
 Sphinx==1.6.5
 sphinxcontrib-websupport==1.0.1
-stestr==2.0.0
+stestr==2.1.0
 testrepository==0.0.18
 testresources==2.0.0
 testscenarios==0.4

test-requirements.txt

@@ -6,7 +6,7 @@ fixtures>=3.0.0 # Apache-2.0/BSD
 hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
 mock>=2.0.0 # BSD
 six>=1.10.0 # MIT
-stestr>=2.0.0 # Apache-2.0
+stestr>=2.1.0 # Apache-2.0
 testresources>=2.0.0 # Apache-2.0/BSD
 testscenarios>=0.4 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT

tox.ini

@@ -5,11 +5,15 @@ envlist = py{27,35,36},pep8,docs
 [testenv]
 usedevelop = True
 install_command = pip install {opts} {packages}
-passenv = PBR_INTEGRATION PIPFLAGS PIPVERSION PBRVERSION REPODIR WHEELHOUSE PROJECTS OS_TEST_TIMEOUT OS_STDOUT_CAPTURE OS_STDERR_CAPTURE
+passenv = PBR_INTEGRATION PIPFLAGS PIPVERSION PBRVERSION REPODIR WHEELHOUSE PROJECTS
+setenv =
+  OS_STDOUT_CAPTURE={env:OS_STDOUT_CAPTURE:1}
+  OS_STDERR_CAPTURE={env:OS_STDERR_CAPTURE:1}
+  OS_TEST_TIMEOUT={env:OS_TEST_TIMEOUT:60}
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
   -r{toxinidir}/test-requirements.txt
-commands = stestr run {posargs}
+commands = stestr run --suppress-attachments {posargs}
 
 [testenv:pep8]
 basepython = python3