[MacOS] fix python installation order (#4052)

images/macos/tests/BasicTools.Tests.ps1

@@ -1,5 +1,11 @@
 $os = Get-OSVersion
 
+Describe "Azure CLI" {
+    It "Azure CLI" {
+        "az -v" | Should -ReturnZeroExitCode
+    }
+}
+
 Describe "Carthage" {
     It "Carthage" {
         "carthage version" | Should -ReturnZeroExitCode

images/macos/tests/Powershell.Tests.ps1

@@ -40,10 +40,4 @@ Describe "Powershell" {
             }
         }
     }
-    
-    Context "Azure CLI" {
-        It "Azure CLI" {
-            "az -v" | Should -ReturnZeroExitCode
-        }
-    }
 }

images/macos/tests/Python.Tests.ps1

@@ -41,4 +41,9 @@ Describe "Python" {
         $python3Path = Split-Path (readlink (which python3))
         $pip3Path | Should -BeExactly $python3Path
     }
+
+    It "2to3 symlink does not point to Python 2" {
+        $2to3path = (Get-ChildItem (Get-Command 2to3).Path).Target
+        $2to3path | Should -Not -BeLike '/Frameworks/Python.framework/Versions/2.*'
+    }
 }