distinguish between user supplied and derived manifest on error printing

Signed-off-by: Nico Schottelius <nico@brief.schottelius.org>

cdist/core/manifest.py

@@ -57,6 +57,29 @@ type manifeste is:
     creates: new objects through type emulator
 '''
 
+class NoInitialManifestError(cdist.Error):
+    """
+    Display missing initial manifest:
+        - Display path if user given
+            - try to resolve link if it is a link
+        - Omit path if default (is a linked path in temp directory without
+            much help)
+    """
+
+    def __init__(self, manifest_path, user_supplied):
+        msg_header = "Initial manifest missing"
+
+        if user_supplied:
+            if os.path.islink(manifest_path):
+                self.message = "%s: %s -> %s" (msg_header, manifest_path, os.path.realpath(manifest_path))
+            else:
+                self.message = "%s: %s" (msg_header, manifest_path)
+        else:
+            self.message = "%s" (msg_header)
+
+    def __str__(self):
+        return repr(self.message)
+
 
 class Manifest(object):
     """Executes cdist manifests.
@@ -70,44 +93,47 @@ class Manifest(object):
 
         self.env = {
             'PATH': "%s:%s" % (self.local.bin_path, os.environ['PATH']),
-            '__target_host': self.target_host,
-            '__global': self.local.out_path,
             '__cdist_type_base_path': self.local.type_path, # for use in type emulator
+            '__global': self.local.out_path,
+            '__target_host': self.target_host,
         }
         if self.log.getEffectiveLevel() == logging.DEBUG:
             self.env.update({'__cdist_debug': "yes" })
 
 
-    def env_initial_manifest(self, script):
+    def env_initial_manifest(self, initial_manifest):
         env = os.environ.copy()
         env.update(self.env)
+        env['__cdist_manifest'] = initial_manifest
         env['__manifest'] = self.local.manifest_path
-        env['__cdist_manifest'] = script
 
         return env
 
     def run_initial_manifest(self, initial_manifest=None):
         if not initial_manifest:
             initial_manifest = self.local.initial_manifest
+            user_supplied = False
+        else:
+            user_supplied = True
 
         self.log.info("Running initial manifest " + initial_manifest)
 
         if not os.path.isfile(initial_manifest):
-            raise cdist.Error("Initial manifest is missing: %s" % initial_manifest)
+            raise NoInitialManifestError(initial_manifest, user_supplied)
 
-        self.local.run_script(script, env=self.env_initial_manifest(initial_manifest))
+        self.local.run_script(initial_manifest, env=self.env_initial_manifest(initial_manifest))
 
     def env_type_manifest(self, cdist_object):
         type_manifest = os.path.join(self.local.type_path, cdist_object.cdist_type.manifest_path)
         env = os.environ.copy()
         env.update(self.env)
         env.update({
+            '__cdist_manifest': type_manifest,
             '__manifest': self.local.manifest_path,
             '__object': cdist_object.absolute_path,
             '__object_id': cdist_object.object_id,
             '__object_name': cdist_object.name,
             '__type': cdist_object.cdist_type.absolute_path,
-            '__cdist_manifest': type_manifest,
         })
 
         return env