Convert parser warnings to stdout in haml_lint

This was used in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16648
and this could happen from time to time, so let's just keep it.

config/initializers/parser_patch.rb

-# frozen_literal_string: true
-
-# This works around unnecessary static-analysis warnings that will be
-# fixed via https://github.com/whitequark/parser/pull/528.
-module Parser
-  class << self
-    def warn_syntax_deviation(feature, version)
-      return if ['2.3.8', '2.4.5', '2.5.3'].include?(version)
-
-      warn "warning: parser/current is loading #{feature}, which recognizes"
-      warn "warning: #{version}-compliant syntax, but you are running #{RUBY_VERSION}."
-      warn "warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri."
-    end
-  end
-end

lib/tasks/haml-lint.rake

@@ -2,5 +2,16 @@ unless Rails.env.production?
   require 'haml_lint/rake_task'
   require 'haml_lint/inline_javascript'
 
+  # Workaround for warnings from parser/current
+  # Keep it even if it no longer emits any warnings,
+  # because we'll still see warnings in console/server anyway,
+  # and we don't need to break static-analysis for this.
+  task :haml_lint do
+    require 'parser'
+    def Parser.warn(*args)
+      puts(*args) # static-analysis ignores stdout if status is 0
+    end
+  end
+
   HamlLint::RakeTask.new
 end