Re-added non-generated errors to a separate file.

Author: dblock

lib/slack-ruby-client.rb

@@ -28,6 +28,7 @@
 require_relative 'slack/web/api/errors/too_many_requests_error'
 require_relative 'slack/web/api/error'
 require_relative 'slack/web/api/errors'
+require_relative 'slack/web/api/errors/internal_error'
 require_relative 'slack/web/faraday/response/raise_error'
 require_relative 'slack/web/faraday/response/wrap_error'
 require_relative 'slack/web/faraday/connection'

lib/slack/web/api/errors/internal_error.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+module Slack
+  module Web
+    module Api
+      module Errors
+        class ServerError < InternalError; end
+        class ParsingError < ServerError; end
+        class HttpRequestError < ServerError; end
+        class TimeoutError < HttpRequestError; end
+        class UnavailableError < HttpRequestError; end
+      end
+    end
+  end
+end