deviantart: fix artist finder for artist names with underscores.

Fix the artist finder for urls like this:

  https://orig00.deviantart.net/4274/f/2010/230/8/a/pkmn_king_and_queen_by_mikoto_chan.jpg

that don't contain a deviantart id but do contain the artist name.

app/logical/sources/strategies/deviant_art.rb

@@ -182,7 +182,7 @@ module Sources
 
       def self.artist_name_from_url(url)
         if url =~ ASSET || url =~ PATH_ART || url =~ PATH_PROFILE
-          $~[:artist]
+          $~[:artist].try(:dasherize)
         elsif url !~ RESERVED_SUBDOMAINS && (url =~ SUBDOMAIN_ART || url =~ SUBDOMAIN_PROFILE)
           $~[:artist]
         else

test/unit/sources/deviantart_test.rb

@@ -82,6 +82,16 @@ module Sources
       end
     end
 
+    context "A source for a *.deviantart.net/*/:title_by_:artist.jpg url artist name containing underscores" do
+      should "find the correct artist" do
+        @site = Sources::Strategies.find("https://orig00.deviantart.net/4274/f/2010/230/8/a/pkmn_king_and_queen_by_mikoto_chan.jpg")
+        @artist = FactoryBot.create(:artist, name: "mikoto-chan", url_string: "https://www.deviantart.com/mikoto-chan")
+
+        assert_equal("mikoto-chan", @site.artist_name)
+        assert_equal([@artist], @site.artists)
+      end
+    end
+
     context "The source for a *.deviantart.net/*/:title_by_:artist.jpg url" do
       setup do
         @url = "http://fc08.deviantart.net/files/f/2007/120/c/9/cool_like_me_by_47ness.jpg"