reformatted the output for missing templates

the environment can now also be stored in the manifest.yml file (least preceedence)

scripts/packme

@@ -19,11 +19,14 @@ from packme import Packman, __version__
 class NotSudo(Exception):
     pass
 
-def clean_templates_dir(templates_base_dir: str):
+def clean_templates_dir(templates_base_dir: str = None):
     """Removes all manifest.json files, packer_cache and builds directories found in
     templates directory
     """
 
+    if templates_base_dir is None:
+        templates_base_dir = "templates"
+
     template_dirs = glob.glob(os.path.join(templates_base_dir,"*"))
 
     for template_dir in template_dirs:

src/packme/PackerTemplate.py

@@ -29,8 +29,14 @@ class PackerTemplate:
         self._packages_base_dir = packages_base_dir
         self._templates_base_dir = templates_base_dir
 
+        # First check whether the manifest contains an environment section
+        self._environment = yaml_node.get("environment", {})
+
+        # Then update this environment with the one found in environment.yml file
         environment_file = os.path.join(self._templates_base_dir,self._name,"environment.yml")
         self._read_environment_file(environment_file)
+
+        # Finally take the global environment as the one with highest precedence
         self._environment.update(os.environ)
 
         # Fetch the 'packer' node
@@ -284,7 +290,7 @@ class PackerTemplate:
 
         # If there are some undefined templates, stop here.
         if undefined:
-            print(f'The following variables are undefined: {undefined!r}')
+            print(f'The following templates could not rendered: {sorted(undefined)!r}')
             sys.exit(1)
         
         template = env.from_string(stringified_node)