docs: def _bootstrap_yum(
          root,
          pkg_confs='/etc/yum*',
          pkgs=None,
          exclude_pkgs=None,
          epel_url=EPEL_URL,
      ):
      '''
      Bootstrap an image using the yum tools
  
      root
          The root of the image to install to. Will be created as a directory if
          it does not exist. (e.x.: /root/arch)
  
      pkg_confs
          The location of the conf files to copy into the image, to point yum
          to the right repos and configuration.
  
      pkgs
          A list of packages to be installed on this image. For RedHat, this
          will include ``yum``, ``centos-release`` and ``iputils`` by default.
  
      exclude_pkgs
          A list of packages to be excluded. If you do not want to install the
          defaults, you need to include them in this list.
  
      epel_url
          The URL to download the EPEL release package from.
  
      TODO: Set up a pre-install overlay, to copy files into /etc/ and so on,
          which are required for the install to work.
      '''
      if pkgs is None:
          pkgs = []
      elif isinstance(pkgs, six.string_types):
          pkgs = pkgs.split(',')
  
      default_pkgs = ('yum', 'centos-release', 'iputils')
      for pkg in default_pkgs:
          if pkg not in pkgs:
              pkgs.append(pkg)
  
      if exclude_pkgs is None:
          exclude_pkgs = []
      elif isinstance(exclude_pkgs, six.string_types):
          exclude_pkgs = exclude_pkgs.split(',')
  
      for pkg in exclude_pkgs:
          pkgs.remove(pkg)
  
      _make_nodes(root)
      release_files = [rf for rf in os.listdir('/etc') if rf.endswith('release')]
      __salt__['cmd.run']('cp /etc/resolv/conf {rfs} {root}/etc'.format(root=_cmd_quote(root), rfs=' '.join(release_files)))
      __salt__['cmd.run']('cp -r {rfs} {root}/etc'.format(root=_cmd_quote(root), rfs=' '.join(release_files)))
      __salt__['cmd.run']('cp -r {confs} {root}/etc'.format(root=_cmd_quote(root), confs=_cmd_quote(pkg_confs)))
  
      yum_args = ['yum', 'install', '--installroot={0}'.format(_cmd_quote(root)), '-y'] + pkgs
      __salt__['cmd.run'](yum_args, python_shell=False)
  
      if 'epel-release' not in exclude_pkgs:
          __salt__['cmd.run'](
              ('rpm', '--root={0}'.format(_cmd_quote(root)), '-Uvh', epel_url),
              python_shell=False
          )