fixed bad variable name

src/packme/PackerTemplate.py

@@ -207,7 +207,7 @@ class PackerTemplate:
         else:
             packages_dir = []
             for package in packages:
-                package_dir = os.path.join(self._packages_dir,package)
+                package_dir = os.path.join(self._packages_root_dir,package)
                 if os.path.exists(package_dir) and os.path.isdir(package_dir):
                     packages_dir.append(package_dir)