exe/conoha in conoha-0.3.1 vs exe/conoha in conoha-0.4.0

@@ -32,10 +32,16 @@
 
 case subcommand
 when 'version', '--version', '-v'
   puts ConohaVersion::ITSELF
 when 'authenticate'
-  Conoha.authenticate!
+  begin
+    Conoha.authenticate!
+  rescue => e
+    STDERR.puts "Failed to authenticate."
+    STDERR.puts "Retry after modifying \"~/.conoha-config.json\"."
+    exit 1
+  end
   puts 'Succeeded!'
 when 'vpslist'
   pp Conoha.vps_list
 when 'status'
   exit 1 if ARGV.size != 1