old_contents: import codecs
  import hashlib
  import json
  import logging
  import os
  import sys
  
  import concurrent.futures
  
  from .const import DEFAULT_MAX_WORKERS
  
  
  log = logging.getLogger(__name__)
  
  
  def parallel_execute(command, containers, doing_msg, done_msg, **options):
      """
      Execute a given command upon a list of containers in parallel.
      """
      max_workers = os.environ.get('COMPOSE_MAX_WORKERS', DEFAULT_MAX_WORKERS)
      stream = codecs.getwriter('utf-8')(sys.stdout)
      lines = []
  
      for container in containers:
          write_out_msg(stream, lines, container.name, doing_msg)
  
      def container_command_execute(container, command, **options):
          return getattr(container, command)(**options)
  
      with concurrent.futures.ThreadPoolExecutor(max_workers=max_workers) as executor:
          future_container = {
              executor.submit(
                  container_command_execute,
                  container,
                  command,
                  **options
              ): container for container in containers
          }
  
          for future in concurrent.futures.as_completed(future_container):
              container = future_container[future]
              write_out_msg(stream, lines, container.name, done_msg)
  
  
  def write_out_msg(stream, lines, container_name, msg):
      """
      Using special ANSI code characters we can write out the msg over the top of
      a previous status message, if it exists.
      """
      if container_name in lines:
          position = lines.index(container_name)
          diff = len(lines) - position
          # move up
          stream.write("%c[%dA" % (27, diff))
          # erase
          stream.write("%c[2K\r" % 27)
          stream.write("{}: {} \n".format(container_name, msg))
          # move back down
          stream.write("%c[%dB" % (27, diff))
      else:
          diff = 0
          lines.append(container_name)
          stream.write("{}: {}... \r\n".format(container_name, msg))
  
      stream.flush()
  
  
  def json_hash(obj):
      dump = json.dumps(obj, sort_keys=True, separators=(',', ':'))
      h = hashlib.sha256()
      h.update(dump)
      return h.hexdigest()
  
new_contents: import codecs
  import hashlib
  import json
  import logging
  import os
  import sys
  
  from docker.errors import APIError
  import concurrent.futures
  
  from .const import DEFAULT_MAX_WORKERS
  
  
  log = logging.getLogger(__name__)
  
  
  def parallel_execute(command, containers, doing_msg, done_msg, **options):
      """
      Execute a given command upon a list of containers in parallel.
      """
      max_workers = os.environ.get('COMPOSE_MAX_WORKERS', DEFAULT_MAX_WORKERS)
      stream = codecs.getwriter('utf-8')(sys.stdout)
      lines = []
      errors = {}
  
      for container in containers:
          write_out_msg(stream, lines, container.name, doing_msg)
  
      def container_command_execute(container, command, **options):
          try:
              getattr(container, command)(**options)
          except APIError as e:
              errors[container.name] = e.explanation
  
      with concurrent.futures.ThreadPoolExecutor(max_workers=max_workers) as executor:
          future_container = {
              executor.submit(
                  container_command_execute,
                  container,
                  command,
                  **options
              ): container for container in containers
          }
  
          for future in concurrent.futures.as_completed(future_container):
              container = future_container[future]
              write_out_msg(stream, lines, container.name, done_msg)
  
      if errors:
          for container in errors:
              stream.write("ERROR: for {}  {} \n".format(container, errors[container]))
  
  
  def write_out_msg(stream, lines, container_name, msg):
      """
      Using special ANSI code characters we can write out the msg over the top of
      a previous status message, if it exists.
      """
      if container_name in lines:
          position = lines.index(container_name)
          diff = len(lines) - position
          # move up
          stream.write("%c[%dA" % (27, diff))
          # erase
          stream.write("%c[2K\r" % 27)
          stream.write("{}: {} \n".format(container_name, msg))
          # move back down
          stream.write("%c[%dB" % (27, diff))
      else:
          diff = 0
          lines.append(container_name)
          stream.write("{}: {}... \r\n".format(container_name, msg))
  
      stream.flush()
  
  
  def json_hash(obj):
      dump = json.dumps(obj, sort_keys=True, separators=(',', ':'))
      h = hashlib.sha256()
      h.update(dump)
      return h.hexdigest()
  
subject: Add in error handling