old_contents: """
  Provides a base class for a 'dummy' setup.py command that has no functionality
  (probably due to a missing requirement).  This dummy command can raise an
  exception when it is run, explaining to the user what dependencies must be met
  to use this command.
  
  The reason this is at all tricky is that we want the command to be able to
  provide this message even when the user passes arguments to the command.  If we
  don't know ahead of time what arguments the command can take, this is
  difficult, because distutils does not allow unknown arguments to be passed to a
  setup.py command.  This hacks around that restriction to provide a useful error
  message even when a user passes arguments to the dummy implementation of a
  command.
  
  Use this like:
  
      try:
          from some_dependency import SetupCommand
      except ImportError:
          from ._dummy import _DummyCommand
  
          class SetupCommand(_DummyCommand):
              description = \
                  'Implementation of SetupCommand from some_dependency; '
                  'some_dependency must be installed to run this command'
  
              # This is the message that will be raised when a user tries to
              # run this command--define it as a class attribute.
              error_msg = \
                  "The 'setup_command' command requires the some_dependency "
                  "package to be installed and importable."
  """
  
  import sys
  from setuptools import Command
  from distutils.errors import DistutilsArgError
  from textwrap import dedent
  
  
  class _DummyCommandMeta(type):
      """
      Causes an exception to be raised on accessing attributes of a command class
      so that if ``./setup.py command_name`` is run with additional command-line
      options we can provide a useful error message instead of the default that
      tells users the options are unrecognized.
      """
  
      def __init__(cls, name, bases, members):
          if bases == (Command, object):
              # This is the _DummyCommand base class, presumably
              return
  
          if not hasattr(cls, 'description'):
              raise TypeError(
                  "_DummyCommand subclass must have a 'description' "
                  "attribute.")
  
          if not hasattr(cls, 'error_msg'):
              raise TypeError(
                  "_DummyCommand subclass must have an 'error_msg' "
                  "attribute.")
  
      def __getattribute__(cls, attr):
          if attr in ('description', 'error_msg'):
              # Allow cls.description to work so that `./setup.py
              # --help-commands` still works
              return super(_DummyCommandMeta, cls).__getattribute__(attr)
  
          raise DistutilsArgError(cls.error_msg)
  
  
  class _DummyCommand(Command, object, metaclass=_DummyCommandMeta):
      pass
  
new_contents: """
  Provides a base class for a 'dummy' setup.py command that has no functionality
  (probably due to a missing requirement).  This dummy command can raise an
  exception when it is run, explaining to the user what dependencies must be met
  to use this command.
  
  The reason this is at all tricky is that we want the command to be able to
  provide this message even when the user passes arguments to the command.  If we
  don't know ahead of time what arguments the command can take, this is
  difficult, because distutils does not allow unknown arguments to be passed to a
  setup.py command.  This hacks around that restriction to provide a useful error
  message even when a user passes arguments to the dummy implementation of a
  command.
  
  Use this like:
  
      try:
          from some_dependency import SetupCommand
      except ImportError:
          from ._dummy import _DummyCommand
  
          class SetupCommand(_DummyCommand):
              description = \
                  'Implementation of SetupCommand from some_dependency; '
                  'some_dependency must be installed to run this command'
  
              # This is the message that will be raised when a user tries to
              # run this command--define it as a class attribute.
              error_msg = \
                  "The 'setup_command' command requires the some_dependency "
                  "package to be installed and importable."
  """
  
  import sys
  from setuptools import Command
  from distutils.errors import DistutilsArgError
  from textwrap import dedent
  
  
  class _DummyCommandMeta(type):
      """
      Causes an exception to be raised on accessing attributes of a command class
      so that if ``./setup.py command_name`` is run with additional command-line
      options we can provide a useful error message instead of the default that
      tells users the options are unrecognized.
      """
  
      def __init__(cls, name, bases, members):
          if bases == (Command, object):
              # This is the _DummyCommand base class, presumably
              return
  
          if not hasattr(cls, 'description'):
              raise TypeError(
                  "_DummyCommand subclass must have a 'description' "
                  "attribute.")
  
          if not hasattr(cls, 'error_msg'):
              raise TypeError(
                  "_DummyCommand subclass must have an 'error_msg' "
                  "attribute.")
  
      def __getattribute__(cls, attr):
          if attr in ('description', 'error_msg') or attr.startswith('_'):
              # Allow cls.description to work so that `./setup.py
              # --help-commands` still works
              return super(_DummyCommandMeta, cls).__getattribute__(attr)
  
          raise DistutilsArgError(cls.error_msg)
  
  
  class _DummyCommand(Command, object, metaclass=_DummyCommandMeta):
      pass
  
subject: Make _DummyCommand not show the custom error message for hidden attributes, since this can interfere with e.g. pytest test collection (which looks for __module__ attributes on objects), and the errors were only meant to be shown for command options, which should be public