Parse out -PACKERSPACE- before looking for exec

config.go

@@ -267,6 +267,14 @@ func (c *config) discoverInternalComponents() error {
 func (c *config) pluginClient(path string) *plugin.Client {
 	originalPath := path
 
+	// Check for special case using `packer plugin PLUGIN`
+	args := []string{}
+	if strings.Contains(path, PACKERSPACE) {
+		parts := strings.Split(path, PACKERSPACE)
+		path = parts[0]
+		args = parts[1:]
+	}
+
 	// First attempt to find the executable by consulting the PATH.
 	path, err := exec.LookPath(path)
 	if err != nil {
@@ -282,14 +290,6 @@ func (c *config) pluginClient(path string) *plugin.Client {
 		}
 	}
 
-	// Check for special case using `packer plugin PLUGIN`
-	args := []string{}
-	if strings.Contains(path, PACKERSPACE) {
-		parts := strings.Split(path, PACKERSPACE)
-		path = parts[0]
-		args = parts[1:]
-	}
-
 	// If everything failed, just use the original path and let the error
 	// bubble through.
 	if path == "" {