Fix #296: ArgumentError with default error formatter.

CHANGELOG.markdown

@@ -1,6 +1,7 @@
 0.2.4 (Next Release)
 ====================
 
+* [#296](https://github.com/intridea/grape/issues/296): Fix: ArgumentError with default error formatter - [@dblock](https://github.com/dblock).
 * Your contribution here.
 
 0.2.3 (24/12/2012)

lib/grape/error_formatter/base.rb

@@ -18,7 +18,7 @@ def formatter_for(api_format, options = {})
           spec = formatters(options)[api_format]
           case spec
           when nil
-            lambda { |message, backtrace, options| message }
+            Grape::ErrorFormatter::Txt
           when Symbol
             method(spec)
           else

spec/grape/api_spec.rb

@@ -875,7 +875,7 @@ class CommunicationError < RuntimeError; end
     end
   end
 
-  describe ".format for error" do
+  describe ".error_format" do
     it 'should rescue all errors and return :txt' do
       subject.rescue_from :all
       subject.format :txt
@@ -896,6 +896,17 @@ class CommunicationError < RuntimeError; end
       last_response.body.start_with?("rain!\r\n").should be_true
     end
 
+    it 'should rescue all errors with a default formatter' do
+      subject.default_format :foo
+      subject.content_type :foo, "text/foo"
+      subject.rescue_from :all
+      subject.get '/exception' do
+        raise "rain!"
+      end
+      get '/exception.foo'
+      last_response.body.should start_with "rain!"
+    end
+
     context "class" do
       before :each do
         class CustomErrorFormatter