Improve Yahoo error handling.

Add test and display Yahoo's error message in warning.

lib/geocoder/lookups/yahoo.rb

@@ -21,7 +21,7 @@ module Geocoder::Lookup
           return []
         end
       else
-        warn "Yahoo Geocoding API error: #{doc['responsecode']}."
+        warn "Yahoo Geocoding API error: #{doc['responsecode']} (#{doc['reason']})."
         return []
       end
     end

test/fixtures/yahoo_error.json

+{"bossresponse":{"responsecode":"6000","reason":"internal error"}}

test/services_test.rb

@@ -82,6 +82,14 @@ class ServicesTest < Test::Unit::TestCase
     assert_equal [], Geocoder.search("no results")
   end
 
+  def test_yahoo_error
+    Geocoder::Configuration.lookup = :yahoo
+    # keep test output clean: suppress timeout warning
+    orig = $VERBOSE; $VERBOSE = nil
+    assert_equal [], Geocoder.search("error")
+    $VERBOSE = orig
+  end
+
   def test_yahoo_result_components
     Geocoder::Configuration.lookup = :yahoo
     result = Geocoder.search("madison square garden").first

test/test_helper.rb

@@ -104,6 +104,7 @@ module Geocoder
         raise SocketError if query.text == "socket_error"
         file = case query.text
           when "no results"; :no_results
+          when "error";      :error
           else               :madison_square_garden
         end
         read_fixture "yahoo_#{file}.json"