2 files changed, 38 insertions, 1 deletions
diff --git a/lib/rubygems/remote_fetcher.rb b/lib/rubygems/remote_fetcher.rb
index ea8d3f9d1f..5b83dc6f6f 100644
--- a/lib/rubygems/remote_fetcher.rb
+++ b/lib/rubygems/remote_fetcher.rb
@@ -237,7 +237,9 @@ class Gem::RemoteFetcher
 
       fetch_http(location, last_modified, head, depth + 1)
     else
-      raise FetchError.new("bad response #{response.message} #{response.code}", uri)
+      custom_error = response["X-Error-Message"]
+      error_detail = custom_error || response.message
+      raise FetchError.new("Bad response #{error_detail} #{response.code}", uri)
     end
   end
 
diff --git a/test/rubygems/test_gem_remote_fetcher.rb b/test/rubygems/test_gem_remote_fetcher.rb
index 9228193152..c35da2fc5a 100644
--- a/test/rubygems/test_gem_remote_fetcher.rb
+++ b/test/rubygems/test_gem_remote_fetcher.rb
@@ -643,6 +643,41 @@ class TestGemRemoteFetcher < Gem::TestCase
     end
   end
 
+  def test_fetch_http_with_custom_error_header
+    fetcher = Gem::RemoteFetcher.new nil
+    @fetcher = fetcher
+    url = "http://gems.example.com/error"
+
+    def fetcher.request(uri, request_class, last_modified = nil)
+      res = Gem::Net::HTTPBadRequest.new nil, 403, "Forbidden"
+      res.add_field "X-Error-Message", "Component blocked by policy"
+      res
+    end
+
+    e = assert_raise Gem::RemoteFetcher::FetchError do
+      fetcher.fetch_http Gem::URI.parse(url)
+    end
+
+    assert_equal "Bad response Component blocked by policy 403 (#{url})", e.message
+  end
+
+  def test_fetch_http_without_custom_error_header
+    fetcher = Gem::RemoteFetcher.new nil
+    @fetcher = fetcher
+    url = "http://gems.example.com/error"
+
+    def fetcher.request(uri, request_class, last_modified = nil)
+      res = Gem::Net::HTTPBadRequest.new nil, 403, "Forbidden"
+      res
+    end
+
+    e = assert_raise Gem::RemoteFetcher::FetchError do
+      fetcher.fetch_http Gem::URI.parse(url)
+    end
+
+    assert_equal "Bad response Forbidden 403 (#{url})", e.message
+  end
+
   private
 
   def assert_error(exception_class = Exception)