Format error messages in short style

lib/droonga/dispatcher.rb

@@ -31,20 +31,19 @@ class Dispatcher
 
     class MissingDatasetParameter < ErrorMessages::BadRequest
       def initialize
-        super("\"dataset\" must be specified.")
+        super("Missing required parameter: <dataset>")
       end
     end
 
     class UnknownDataset < ErrorMessages::NotFound
       def initialize(dataset)
-        super("The dataset #{dataset.inspect} does not exist.")
+        super("Unknown dataset: <#{dataset}>")
       end
     end
 
     class UnknownCommand < ErrorMessages::BadRequest
       def initialize(command, dataset)
-        super("The command #{command.inspect} is not available " +
-                "for the dataset #{dataset.inspect}.")
+        super("[#{dataset}] Handler not found for the type: <#{command}>")
       end
     end
 

lib/droonga/plugin_registry.rb

@@ -19,7 +19,7 @@ class PluginRegistry
 
     class UnknownPlugin < Error
       def initialize(name, klass)
-        super("Unknown plugin \"#{name}\" is specified for #{klass}.")
+        super("[#{klass}] Plugin not found: <#{name}>")
       end
     end
 

lib/droonga/searcher.rb

@@ -32,15 +32,15 @@ def initialize
 
     class MissingSourceParameter < ErrorMessages::BadRequest
       def initialize(query, queries)
-        super("The query #{query.inspect} has no source. " +
+        super("[#{query}] No source is specified. " +
                 "Query must have a valid source.",
               queries)
       end
     end
 
     class UnknownSource < ErrorMessages::NotFound
       def initialize(source, queries)
-        super("The source #{source.inspect} does not exist. " +
+        super("Source not found: <#{source}> " +
                 "It must be a name of an existing table or another query.",
               queries)
       end