Don't suppress Twitter::Error::Forbidden in #follow and #follow!

Closes #502.

lib/twitter/error.rb

@@ -19,6 +19,7 @@ module Codes
       OVER_CAPACITY                = 130
       INTERNAL_ERROR               = 131
       OAUTH_TIMESTAMP_OUT_OF_RANGE = 135
+      FOLLOW_ALREADY_REQUESTED     = 160
       FOLLOW_LIMIT_EXCEEDED        = 161
       PROTECTED_STATUS             = 179
       OVER_UPDATE_LIMIT            = 185

lib/twitter/rest/api/friends_and_followers.rb

@@ -137,13 +137,7 @@ def follow(*args)
         def follow!(*args)
           arguments = Twitter::Arguments.new(args)
           arguments.flatten.threaded_map do |user|
-            begin
-              object_from_response(Twitter::User, :post, '/1.1/friendships/create.json', merge_user(arguments.options, user))
-            rescue Twitter::Error::Forbidden
-              # This error will be raised if the user doesn't have permission to
-              # follow list_member, for whatever reason.
-              next
-            end
+            object_from_response(Twitter::User, :post, '/1.1/friendships/create.json', merge_user(arguments.options, user))
           end.compact
         end
         alias_method :create_friendship!, :follow!

spec/fixtures/forbidden.json

@@ -0,0 +1 @@
+{"errors":[{"code":160,"message":"You've already requested to follow %s."}]}

spec/helper.rb

@@ -8,7 +8,7 @@
 
 SimpleCov.start do
   add_filter '/spec/'
-  minimum_coverage(99.07)
+  minimum_coverage(99.13)
 end
 
 require 'twitter'

spec/twitter/rest/api/friends_and_followers_spec.rb

@@ -352,6 +352,14 @@
       expect(a_post('/1.1/friendships/create.json').with(:body => {:screen_name => 'sferik'})).to have_been_made
     end
   end
+  context 'with a forbidden error' do
+    before do
+      stub_post('/1.1/friendships/create.json').with(:body => {:screen_name => 'sferik'}).to_return(:status => 403, :body => fixture('forbidden.json'), :headers => {:content_type => 'application/json; charset=utf-8'})
+    end
+    it 'raises an exception' do
+      expect { @client.follow!('sferik') }.to raise_error(Twitter::Error::Forbidden)
+    end
+  end
 
   describe '#unfollow' do
     before do