commit a748b173a004c0a42dda124de07c336fe6161a48
Author: wu.shiming <wushiming@yovole.com>
Date:   Fri Oct 9 10:42:27 2020 +0800

    Dep's should be restricted by upper-constraints
    
    Tox trying to install latest versions for building docs which may
    not be supported by stable and lower branches, so should be
    restricted by respective version's upper-constraints.txt
    
    Change-Id: Ica00ee97b12cc3074fbc6394923ed82309fe7466

diff --git a/tox.ini b/tox.ini
index 2e79a80..9c6477c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -44,7 +44,9 @@ commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasen
 commands = oslo-config-generator --config-file=etc/ceilometer/ceilometer-config-generator.conf
 
 [testenv:docs]
-deps = -r{toxinidir}/doc/requirements.txt
+deps =
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -b html doc/source doc/build/html
 setenv = PYTHONHASHSEED=0