The Flymake test suite fails if the "rubocop" program is installed,
because the ruby-flymake-rubocop backend is selected automatically by
ruby-flymake-auto. The test was designed for ruby-flymake-simple,
tough, and fails.
* test/lisp/progmodes/flymake-tests.el (ruby-backend): Ensure
this test runs exclusively with the ruby-flymake-simple backend.