module ParallelTests::Tasks

- simple system "set -o pipefail" returns nil even though set -o pipefail exists with 0
- 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 = %{(grep -v #{Shellwords.escape(ignore_regex)} || true)}
  # remove nil values (ex: #purge_before_load returns nil)
  command.compact!
  if system('/bin/bash', '-c', "#{activate_pipefail} 2>/dev/null")
    shell_command = "#{activate_pipefail} && (#{Shellwords.shelljoin(command)}) | #{remove_ignored_lines}"
    ['/bin/bash', '-c', shell_command]
  else
    command
  end
end