Allow component specific config to not exist

Instead of blowing up when component specific configuration (or
general configuration) is not found, just have it not be found and
then if not found not be merged (or cached) in to the configuration
dictionary eventually returned.

Change-Id: Iac3a52d9521dec82ea513f243736511c64a7e59f

anvil/cfg.py

@@ -17,12 +17,16 @@
 import re
 
 from anvil import exceptions
+from anvil import log as logging
 from anvil import origins as _origins
 from anvil import settings
 from anvil import shell as sh
 from anvil import utils
 
 
+LOG = logging.getLogger(__name__)
+
+
 class YamlMergeLoader(object):
     """Holds merging process component options (based on Yaml reference loader).
 
@@ -65,7 +69,13 @@ class YamlMergeLoader(object):
             if persona is not None:
                 # Note: any additional redefines could be added here.
                 persona_specific = persona.component_options.get(component, {})
-                self._base_loader.update_cache(conf, persona_specific)
+                try:
+                    self._base_loader.update_cache(conf, persona_specific)
+                except exceptions.YamlConfigNotFoundException:
+                    LOG.warn("Unable to update the loaders cache with"
+                             " component '%s' configuration using"
+                             " persona specific data: %s", conf,
+                             persona_specific, exc_info=True)
 
     def load(self, distro, component, persona=None, origins_patch=None):
         # NOTE (vnovikov): applying takes place before loading reference links
@@ -81,16 +91,21 @@ class YamlMergeLoader(object):
                 origins_opts = origins[component]
             except KeyError:
                 pass
-        general_component_opts = self._base_loader.load('general')
-        component_specific_opts = self._base_loader.load(component)
+
+        component_opts = []
+        for conf in ('general', component):
+            try:
+                component_opts.append(self._base_loader.load(conf))
+            except exceptions.YamlConfigNotFoundException:
+                LOG.warn("Unable to find component specific configuration"
+                         " for component '%s'", conf, exc_info=True)
 
         # NOTE (vnovikov): merge order is the same as arguments order below.
         merged_opts = utils.merge_dicts(
             dir_opts,
             distro_opts,
             origins_opts,
-            general_component_opts,
-            component_specific_opts,
+            *component_opts
         )
         return merged_opts
 
@@ -245,8 +260,6 @@ class YamlRefLoader(object):
 
     def update_cache(self, conf, dict2update):
         self._cache(conf)
-        #for k, v in dict2update.items():
-        #    self._cached[conf][k] = v
 
         # NOTE (vnovikov): should remove obsolete processed data
         self._cached[conf].update(dict2update)