Enhancement: Adjust doctor command

lib/jekyll/commands/doctor.rb

@@ -39,19 +39,27 @@ def healthy?(site)
             !conflicting_urls(site),
             !urls_only_differ_by_case(site),
             proper_site_url?(site),
-            properly_gathered_posts?(site),
+            properly_gathered_drafts_and_posts?(site),
           ].all?
         end
 
-        def properly_gathered_posts?(site)
+        def properly_gathered_drafts_and_posts?(site)
           return true if site.config["collections_dir"].empty?
-          posts_at_root = site.in_source_dir("_posts")
-          return true unless File.directory?(posts_at_root)
+
+          directories = ["_drafts", "_posts"]
+
+          directories.select do |directory|
+            File.directory?(site.in_source_dir(directory))
+          end
+
+          return true if directories.empty?
+
           Jekyll.logger.warn "Warning:",
-            "Detected '_posts' directory outside custom `collections_dir`!"
+            "Detected '#{directories.join("', '")}' directory outside custom `collections_dir`!"
           Jekyll.logger.warn "",
-            "Please move '#{posts_at_root}' into the custom directory at " \
+            "Please move '#{directories.join("', '")}' into the custom directory at " \
             "'#{site.in_source_dir(site.config["collections_dir"])}'"
+
           false
         end