packer: fix splitting error message on pathsep

packer/plugin_folders.go

@@ -13,13 +13,15 @@ import (
 	"github.com/hashicorp/packer-plugin-sdk/pathing"
 )
 
+var pathSep = fmt.Sprintf("%c", os.PathListSeparator)
+
 // PluginFolder returns the known plugin folder based on system.
 func PluginFolder() (string, error) {
 	if packerPluginPath := os.Getenv("PACKER_PLUGIN_PATH"); packerPluginPath != "" {
-		if strings.ContainsRune(packerPluginPath, os.PathListSeparator) {
+		if strings.Contains(packerPluginPath, pathSep) {
 			return "", fmt.Errorf("Multiple paths are no longer supported for PACKER_PLUGIN_PATH.\n"+
 				"This should be defined as one of the following options for your environment:"+
-				"\n* PACKER_PLUGIN_PATH=%v", strings.Join(strings.Split(packerPluginPath, ":"), "\n* PACKER_PLUGIN_PATH="))
+				"\n* PACKER_PLUGIN_PATH=%v", strings.Join(strings.Split(packerPluginPath, pathSep), "\n* PACKER_PLUGIN_PATH="))
 		}
 
 		return packerPluginPath, nil