Create a bucket if one doesn't exist.

This method prevents excessive calls to the S3 API, creating a bucket
only if the store method fails with a NoSuchBucket error instead of
asking for the bucket before each request.

lib/paperclip/storage/s3.rb

@@ -133,6 +133,10 @@ module Paperclip
         return file
       end
 
+      def create_bucket
+        AWS::S3::Bucket.create(bucket_name)
+      end
+
       def flush_writes #:nodoc:
         @queued_for_write.each do |style, file|
           begin
@@ -143,6 +147,9 @@ module Paperclip
                                     {:content_type => instance_read(:content_type),
                                      :access => @s3_permissions,
                                     }.merge(@s3_headers))
+          rescue AWS::S3::NoSuchBucket => e
+            create_bucket
+            retry
           rescue AWS::S3::ResponseError => e
             raise
           end

test/storage_test.rb

@@ -185,6 +185,21 @@ class StorageTest < Test::Unit::TestCase
         end
       end
 
+      context "and saved without a bucket" do
+        setup do
+          class AWS::S3::NoSuchBucket < AWS::S3::ResponseError
+            # Force the class to be created as a proper subclass of ResponseError thanks to AWS::S3's autocreation of exceptions
+          end
+          AWS::S3::Bucket.expects(:create).with("testing")
+          AWS::S3::S3Object.stubs(:store).raises(AWS::S3::NoSuchBucket.new(:message, :response)).then.returns(true)
+          @dummy.save
+        end
+
+        should "succeed" do
+          assert true
+        end
+      end
+
       context "and remove" do
         setup do
           AWS::S3::S3Object.stubs(:exists?).returns(true)