Generated X-Amz-Expires is incorrect when it spans a transition to/off Daylight Savings Time

[egh]

Hi -

It's not clear to me if this is a fog, rails or a carrierwave issue, but I'm starting here.

Carrierwave allows a user to set a fog_authenticated_url_expiration, which can be used to generate a X-Amz-Expires header when requesting an authenticated URL from S3. For example, fog_authenticated_url_expiration is set to 1.week (an ActiveRecord::Duration)

If this duration spans a transition on or off Daylight Savings Time, the wrong X-Amz-Expires header is generated.

See the patch below for a failing test

index c87068a..10a3071 100644
--- a/spec/storage/fog_helper.rb
+++ b/spec/storage/fog_helper.rb
@@ -85,6 +85,26 @@ end
             end
           end
 
+          it "should generate a proper X-Amz-Expires when expires spans a move to DST" do
+            if @provider == 'AWS'
+              Timecop.freeze(Time.at(1477932000)) do |now|
+                expiration = 7 * 24 * 60 * 60 # 1 week
+                allow(@uploader).to receive(:fog_authenticated_url_expiration).and_return(expiration)
+                expect(@fog_file.authenticated_url).to include("X-Amz-Expires=#{expiration.to_s}")
+              end
+            end
+          end
+
+          pending "should generate a proper X-Amz-Expires when expires spans a move to DST and an ActiveRecord::Duration is provided" do
+            if @provider == 'AWS'
+              Timecop.freeze(Time.at(1477932000)) do |now|
+                expiration = 1.week
+                allow(@uploader).to receive(:fog_authenticated_url_expiration).and_return(expiration)
+                expect(@fog_file.authenticated_url).to include("X-Amz-Expires=#{expiration.to_s}")
+              end
+            end
+          end
+
           it "should use a subdomain URL for AWS if the directory is a valid subdomain" do
             if @provider == 'AWS'
               allow(@uploader).to receive(:fog_directory).and_return('assets.site.com')