old_contents: #!/usr/bin/env python2
  
  import argparse
  import multitail
  
  parser = argparse.ArgumentParser()
  parser.add_argument('files', type=str, nargs='+')
  args = parser.parse_args()
  
  for fn, line in multitail.multitail(args.files):
    print("{}: {}".format(fn,line.strip()))
  
new_contents: #!/usr/bin/env python2
  
  import argparse
  import multitail
  import sys
  
  # http://stackoverflow.com/questions/107705
  class Unbuffered(object):
    def __init__(self, stream): self.stream = stream
    def write(self, data): self.stream.write(data); self.stream.flush()
    def __getattr__(self, attr): return getattr(self.stream, attr)
  sys.stdout = Unbuffered(sys.stdout)
  
  parser = argparse.ArgumentParser()
  parser.add_argument('files', type=str, nargs='+')
  args = parser.parse_args()
  
  for fn, line in multitail.multitail(args.files):
    print("{}: {}".format(fn,line.strip()))
  
subject: Disable output buffering.