module ParallelTests::Tasks

- simple system "set -o pipefail" returns nil even though set -o pipefail exists with 0
- do not use ' since run_in_parallel uses them to quote stuff
- defining a new rake task like silence_schema would force users to load parallel_tests in test env
- pipefail is not supported in (zsh)
- pipefail makes pipe fail with exitstatus of first failed command
- sed changes 1 exitstatus to 0
- grep changes 0 exitstatus to 1 if nothing matches
- sed does not support | without -r

normally I'd not do this, but it has been lots of fun and a great learning experience :)
removing certain lines from the output without changing the exit-status
this is a crazy-complex solution for a very simple problem:

def suppress_output(command, ignore_regex)
  activate_pipefail = "set -o pipefail"
  remove_ignored_lines = %Q{(grep -v "#{ignore_regex}" || test 1)}
  if File.executable?('/bin/bash') && system('/bin/bash', '-c', "#{activate_pipefail} 2>/dev/null && test 1")
    # We need to shell escape single quotes (' becomes '"'"') because
    # run_in_parallel wraps command in single quotes
    %Q{/bin/bash -c '"'"'#{activate_pipefail} && (#{command}) | #{remove_ignored_lines}'"'"'}
  else
    command
  end
end