Skip compression in case of error

YUI-Compressor complains too much.
Because compression isn't a crucial step for deployments, we print a
warning and let developers to still deploy and review later the reason
of the problem.

lib/lotus/assets/bundler.rb

@@ -117,6 +117,8 @@ def store_manifest(asset, target)
       # @api private
       def _compress(compressor, asset)
         _write(asset, compressor.compress(::File.read(asset)))
+      rescue => e
+        warn "Skipping compression of: `#{ asset }'\n\nReason: #{ e }"
       end
 
       # @since x.x.x

test/bundler_test.rb

@@ -73,6 +73,16 @@
     manifest.must_be :exist?
   end
 
+  describe "in case of error" do
+    let(:dest)   { TMP.join('broken', 'public') }
+    let(:source) { __dir__ + '/fixtures/broken/public/assets' }
+
+    it "prints the name of the asset that caused the problem" do
+      _, err = capture_subprocess_io { run! }
+      err.must_match "Skipping compression of:"
+    end
+  end
+
   private
 
   def run!

test/fixtures/broken/public/assets/broken.js

@@ -0,0 +1 @@
+// This empty JavaScript causes an error with YUICompressor