Improved error reporting when a parameter cannot be found

 * Fixes #8
 * A error inheriting from VagrantError is raised with a nice
   (an translatable) error message.

lib/nugrant.rb

@@ -7,7 +7,26 @@ class KeyError < IndexError
   end
 end
 
+module Nugrant
+  def self.create_parameters(options)
+    config = Nugrant::Config.new(options)
+
+    return Nugrant::Parameters.new(config)
+  end
+
+  def self.setup_i18n()
+    I18n.load_path << File.expand_path("locales/en.yml", Nugrant.source_root)
+    I18n.reload!
+  end
+
+  def self.source_root
+    @source_root ||= Pathname.new(File.expand_path("../../", __FILE__))
+  end
+end
+
 if defined?(Vagrant)
+  Nugrant.setup_i18n()
+
   case
   when defined?(Vagrant::Plugin::V2)
     require 'nugrant/vagrant/v2/plugin'
@@ -17,11 +36,3 @@ class KeyError < IndexError
     abort("You are trying to use Nugrant with an unsupported Vagrant version [#{Vagrant::VERSION}]")
   end
 end
-
-module Nugrant
-  def self.create_parameters(options)
-    config = Nugrant::Config.new(options)
-
-    return Nugrant::Parameters.new(config)
-  end
-end

lib/nugrant/vagrant/errors.rb

@@ -0,0 +1,15 @@
+require 'vagrant/errors'
+
+module Nugrant
+  module Vagrant
+    module Errors
+      class NugrantVagrantError < ::Vagrant::Errors::VagrantError
+        error_namespace("nugrant.vagrant.errors")
+      end
+
+      class ParameterNotFoundError < NugrantVagrantError
+        error_key(:parameter_not_found)
+      end
+    end
+  end
+end

lib/nugrant/vagrant/v1/config/user.rb

@@ -1,4 +1,5 @@
 require 'nugrant'
+require 'nugrant/vagrant/errors'
 
 module Nugrant
   module Vagrant
@@ -13,10 +14,14 @@ def initialize()
 
           def [](param_name)
             return @parameters[param_name]
+          rescue KeyError
+            raise Errors::ParameterNotFoundError, :key => param_name
           end
 
           def method_missing(method, *args, &block)
             return @parameters.method_missing(method, *args, &block)
+          rescue KeyError
+            raise Errors::ParameterNotFoundError, :key => method
           end
 
           def each(&block)

lib/nugrant/vagrant/v2/config/user.rb

@@ -1,4 +1,5 @@
 require 'nugrant'
+require 'nugrant/vagrant/errors'
 
 module Nugrant
   module Vagrant
@@ -13,10 +14,14 @@ def initialize()
 
           def [](param_name)
             return @parameters[param_name]
+          rescue KeyError
+            raise Errors::ParameterNotFoundError, :key => param_name
           end
 
           def method_missing(method, *args, &block)
             return @parameters.method_missing(method, *args, &block)
+          rescue KeyError
+            raise Errors::ParameterNotFoundError, :key => method
           end
 
           def each(&block)

locales/en.yml

@@ -0,0 +1,10 @@
+en:
+  nugrant:
+    vagrant:
+      errors:
+        parameter_not_found: |-
+          Nugrant: Parameter '%{key}' was not found, is it defined in
+          your .vagrantuser file?
+
+          If you think it should be found, don't hesitate to fill an
+          issue @ https://github.com/maoueh/nugrant/issues.