https://git.ruby-lang.org/ruby.git/commit/?id=4d75346187

From 4d75346187557ae59736ca5739bfae312c285e08 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@r...>
Date: Sat, 3 Aug 2019 14:20:36 +0900
Subject: Refine error message

Highlight failed command and suggest installing the command.
[Bug #16042]

diff --git a/tool/pure_parser.rb b/tool/pure_parser.rb
index 4d5e86e..9ab6638 100755
--- a/tool/pure_parser.rb
+++ b/tool/pure_parser.rb
@@ -4,7 +4,12 @@ BEGIN { https://github.com/ruby/ruby/blob/trunk/tool/pure_parser.rb#L4
 
   colorize = Colorize.new
   file = ARGV.shift
-  unless /\Abison .* (\d+)\.\d+/ =~ IO.popen(ARGV+%w[--version], &:read)
+  begin
+    version = IO.popen(ARGV+%w[--version], &:read)
+  rescue Errno::ENOENT
+    abort "Failed to run `#{colorize.fail ARGV.join(' ')}'; You may have to install it."
+  end
+  unless /\Abison .* (\d+)\.\d+/ =~ version
     puts colorize.fail("not bison")
     exit
   end
-- 
cgit v0.10.2


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