Reuse the docs deps to benefit from constraints
Tox trying to install latest versions for building releasenotes,
which may not be supported by stable and lower branches,
so should be restricted by respective version's upper-constraints.txt
This ps to reuse upper-constraints.txt from docs deps
@@ -77,7 +77,7 @@ commands = oslo-config-generator --config-file=etc/oslo-config-generator/kuryr.c
[testenv:releasenotes]
basepython = python3
-deps = -r{toxinidir}/doc/requirements.txt
+deps = {[testenv:docs]deps}
commands = sphinx-build -a -W -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
[testenv:lower-constraints]
