Update onboarding script and dsc monitor plugin to use python3 over python2 if both versions are present (#1483)

* use python3 over python2 if both versions are installed in dsc metaconfig

* update dsc plugin to use python3 over python2 for TestDscConfiguration.py

* use which instead of command in dsc ruby plugin

Author: NarineM

installer/scripts/omsadmin.sh

@@ -53,11 +53,11 @@ AGENT_MAINTENANCE_MISSING_CONFIG_FILE=4
 AGENT_MAINTENANCE_MISSING_CONFIG=5
 AGENT_MAINTENANCE_ERROR_WRITING_TO_FILE=12
 
-# DSC MetaConfig generation script
-if [ -x "$(command -v python2)" ]; then
-    METACONFIG_PY=/opt/microsoft/omsconfig/Scripts/OMS_MetaConfigHelper.py
-elif [ -x "$(command -v python3)" ]; then
+# DSC MetaConfig generation script. User python3 over python2 if both versions are installed
+if [ -x "$(command -v python3)" ]; then
     METACONFIG_PY=/opt/microsoft/omsconfig/Scripts/python3/OMS_MetaConfigHelper.py
+elif [ -x "$(command -v python2)" ]; then
+    METACONFIG_PY=/opt/microsoft/omsconfig/Scripts/OMS_MetaConfigHelper.py
 else
     # Failure to find python/the correct script path will only break onboarding (just one
     # of omsadmin's numerous functions); exit with failure in the onboard() function instead

source/code/plugins/in_dsc_monitor.rb

@@ -57,11 +57,11 @@ def run_check_install
 
     def get_dsc_status
       begin
-        python = %x(which python2)
+        python = %x(which python3)
         if !python.empty?
-            dsc_status = %x(/opt/microsoft/omsconfig/Scripts/TestDscConfiguration.py)
-        else # assume python3, since /some/ python is an install prereq and we have a rescue below regardless
             dsc_status = %x(/opt/microsoft/omsconfig/Scripts/python3/TestDscConfiguration.py)
+        else # assume python2, since /some/ python is an install prereq and we have a rescue below regardless
+            dsc_status = %x(/opt/microsoft/omsconfig/Scripts/TestDscConfiguration.py)
         end
       rescue => error
         OMS::Log.error_once("Running TestDscConfiguration.py returned error : #{error}")

test/code/plugins/in_dsc_monitor_plugintest.rb

@@ -8,9 +8,9 @@ class DscMonitorTest < Test::Unit::TestCase
   TMP_DIR = File.dirname(__FILE__) + "/../tmp/test_dscmonitor"
   CHECK_IF_DPKG = "which dpkg > /dev/null 2>&1; echo $?" 
   CHECK_DSC_INSTALL = "dpkg --list omsconfig > /dev/null 2>&1; echo $?"
-  CHECK_DSC_STATUS = "/opt/microsoft/omsconfig/Scripts/TestDscConfiguration.py"
-  CHECK_DSC_STATUS_PYTHON_3 = "/opt/microsoft/omsconfig/Scripts/python3/TestDscConfiguration.py"
-  CHECK_PYTHON = "which python2"
+  CHECK_DSC_STATUS = "/opt/microsoft/omsconfig/Scripts/python3/TestDscConfiguration.py"
+  CHECK_DSC_STATUS_PYTHON_2 = "/opt/microsoft/omsconfig/Scripts/TestDscConfiguration.py"
+  CHECK_PYTHON = "which python3"
 
   def setup
     Fluent::Test.setup
@@ -64,8 +64,8 @@ def test_dsc_check_failure_message
       instance.should_receive(:`).with(CHECK_IF_DPKG).and_return(0)
       instance.should_receive(:`).with(CHECK_DSC_INSTALL).and_return(0)
       instance.should_receive(:`).with(CHECK_DSC_STATUS).and_return("Mock DSC config check")
-      instance.should_receive(:`).with(CHECK_DSC_STATUS_PYTHON_3).and_return("Mock DSC config check")
-      instance.should_receive(:`).with(CHECK_PYTHON).and_return("/usr/bin/python2") # as if python2 is installed
+      instance.should_receive(:`).with(CHECK_DSC_STATUS_PYTHON_2).and_return("Mock DSC config check")
+      instance.should_receive(:`).with(CHECK_PYTHON).and_return("/usr/bin/python3") # as if python3 is installed
     end
 
     d = create_driver
@@ -91,8 +91,8 @@ def test_dsc_check_success_emits_no_messages
       instance.should_receive(:`).with(CHECK_IF_DPKG).and_return(0)
       instance.should_receive(:`).with(CHECK_DSC_INSTALL).and_return(0)
       instance.should_receive(:`).with(CHECK_DSC_STATUS).and_return(result)
-      instance.should_receive(:`).with(CHECK_DSC_STATUS_PYTHON_3).and_return(result)
-      instance.should_receive(:`).with(CHECK_PYTHON).and_return("/usr/bin/python2") # as if python2 is installed
+      instance.should_receive(:`).with(CHECK_DSC_STATUS_PYTHON_2).and_return(result)
+      instance.should_receive(:`).with(CHECK_PYTHON).and_return("") # as if python2 is installed
     end
 
     d = create_driver