Normally a rake task won't complete if one of its prerequisites fails. Define a composite task to allow them all to run, capturing exceptions and reporting them only after all have completed.

composite_task.rb

# Take for example a convenience task, all_tests, that runs our app's
# test suite for multiple architectures:
#
#     task :all_tests => [:test_64_bit, :test_32_bit]
#
# Defined as a regular task, Rake will bail out early if
# test_64_bit failed, never getting to the 32 bit tests.
#
# A composite task is almost identical in declaration:
#
#     composite :all_tests => [:test_64_bit, :test_32_bit]
#
# This task will instead run *all* its prerequisites, recording if
# they fail, and only reporting failures once all tasks have completed.
#
class CompositeTask < Rake::Task

  attr_reader :failures

  # Hook into prerequisite invocation to add exception handling
  # to each one.
  def invoke_prerequisites(*args)
    failures = []
    prerequisite_tasks.each do |p|
      p.define_singleton_method(:execute) do |*args|
        begin
          super(*args)
          failures << nil
        rescue => e
          failures << e
        end
      end
    end
    super(*args).tap { @failures = failures }
  end

  # When executing this task, see if any failures were reported
  # and re-raise them.
  def execute(*args)
    super(*args)
    failed_commands = prerequisite_tasks.zip(failures).delete_if { |_, failure| failure.nil? }
    unless failed_commands.empty?
      # TODO: work out how to re-raise more than just the first failure
      raise failed_commands.map { |_, ex| ex }.first
    end
  end

end

def composite(*args, &block)
  CompositeTask.define_task(*args, &block)
end