Ruby’s New Exception Keyword Argumentsexception: false and exception: true In Ruby 2.6, a variety of Kernel methods get a new exception: false or exception: true keyword argument. When Kernel methods fail, some raise an error and some just return nil. This new feature lets you override that default behavior. TL;DR: In Ruby 2.6 these examples will all work: system 'not-a-command', exception: true #