Only install yamllint in py3 env

A new yamllint was released which dropped py2 support.
Zuul servers that have updated their caches will attempt
to install that version, as it is not clamped by upper constraints.

This also attempts to not use site packages.

Partial-Bug: 1922590

Change-Id: I8b2776f4c12447a66743a8b2626aa914969dcd2a
Signed-off-by: albailey <Al.Bailey@windriver.com>

distributedcloud/test-requirements.txt

@@ -21,4 +21,4 @@ tempest-lib>=0.14.0 # Apache-2.0
 pylint==1.9.2;python_version<"3.0" # GPLv2
 pylint==2.3.1;python_version>="3.0" # GPLv2
 PyYAML>=3.1.0
-yamllint>=0.5.2
+yamllint<1.26.1;python_version>="3.0" # GPLv2

distributedcloud/tox.ini

@@ -18,6 +18,7 @@ cgtsclient_src_dir = ../../config/sysinv/cgts-client/cgts-client
 cgcs_patch_src_dir = ../../update/cgcs-patch/cgcs-patch
 
 [testenv]
+sitepackages = False
 install_command = pip install -v -v -v \
     -c https://opendev.org/openstack/requirements/raw/branch/stable/stein/upper-constraints.txt \
     {opts} {packages}
@@ -184,7 +185,6 @@ import_exceptions = dcmanager.common.i18n,dcorch.common.i18n
 
 [testenv:pylint]
 basepython = python3
-sitepackages = False
 deps = {[testenv:py27]deps}
        -e{[dc]cgcs_patch_src_dir}
 

test-requirements.txt

@@ -1,3 +1,3 @@
 PyYAML>=3.1.0
-yamllint>=0.5.2
+yamllint<1.26.1;python_version>="3.0" # GPLv2
 mock>=2.0 # BSD