deviantart: support non-downloadable videos

app/logical/sources/strategies/deviant_art.rb

@@ -90,6 +90,8 @@ module Sources
           api_download[:src]
         elsif api_deviation[:flash].present?
           api_deviation.dig(:flash, :src)
+        elsif api_deviation[:videos].present?
+          api_deviation[:videos].max_by { |x| x[:filesize] }[:src]
         else
           src = api_deviation.dig(:content, :src)
           if deviation_id && deviation_id.to_i <= 790677560 && src =~ /^https:\/\/images-wixmp-/ && src !~ /\.gif\?/

test/unit/sources/deviant_art_test.rb

@@ -264,6 +264,16 @@ module Sources
       end
     end
 
+    context "The source for a non-downloadable video file" do
+      should "return working image url" do
+        @site = Sources::Strategies.find("https://www.deviantart.com/gs-mantis/art/Chen-Goes-Fishing-505847233")
+
+        # md5: 344ac2b9fd5a87982af4b648aa2b2b0d
+        assert_equal("https://wixmp-ed30a86b8c4ca887773594c2.wixmp.com/v/mp4/fe046bc7-4d68-4699-96c1-19aa464edff6/d8d6281-91959e92-214f-4b2d-a138-ace09f4b6d09.1080p.8e57939eba634743a9fa41185e398d00.mp4", @site.image_url)
+        assert_downloaded(9_739_947, @site.image_url)
+      end
+    end
+
     context "The source for an DeviantArt artwork page" do
       setup do
         @site = Sources::Strategies.find("http://noizave.deviantart.com/art/test-post-please-ignore-685436408")