Create a separate tox env for Agent Python 3.6

The requirements for the agent, client, and server are different enough
that any new version requirement for the client or server code will
cause the `py36` environment to fail installation.  This isolates the
use of Python 3.6 so that only the agent requirements are installed.

Author: portante

jenkins/Pipeline.gy

@@ -35,7 +35,7 @@ pipeline {
         stage('Agent Python3.6 Check') {
             steps {
                 echo 'Verify agent side works with Python 3.6'
-                sh 'jenkins/run tox -e py36 -- agent'
+                sh 'jenkins/run tox -e agent-py36 -- agent'
             }
         }
         stage('Linting, Unit Tests, RPM builds') {

tox.ini

@@ -6,7 +6,7 @@ distshare = {toxworkdir}/distshare
 envlist = py39
 
 [testenv]
-description = Lints code and runs all agent and server unit/functional tests
+description = Runs all agent, client, and server unit/functional tests
 install_command = pip install --cache-dir={toxworkdir}/cache --progress-bar off --prefix={envdir} {opts} {packages}
 passenv =
     PY_COLORS
@@ -33,3 +33,10 @@ commands =
     bash -c "{toxinidir}/exec-tests {envdir} {posargs}"
 whitelist_externals =
     bash
+
+[testenv:agent-py36]
+description = Runs all agent unit tests under Python 3.6
+basepython = python3.6
+deps =
+    -r{toxinidir}/agent/requirements.txt
+    -r{toxinidir}/agent/test-requirements.txt