Merge "Do not use multiprocessing.Pool when --processes=1."

def parallel_classify_warnings(warning_lines):

  """Classify all warning lines with num_cpu parallel processes."""

  num_cpu = args.processes

  if num_cpu > 1:

    groups = [[] for x in range(num_cpu)]

    i = 0

    for x in warning_lines:

      i = (i + 1) % num_cpu

    pool = multiprocessing.Pool(num_cpu)

    group_results = pool.map(classify_warnings, groups)

  else:

    group_results = [classify_warnings(warning_lines)]

  for result in group_results:

    for line, pattern_idx, project_idx in result:

      pattern = warn_patterns[pattern_idx]