code: def install_custom_css( destdir, cssfile, resource=PKGNAME ):
      
      ensure_dir_exists( destdir )
      custom = os.path.join( destdir, 'custom.css' )
      prefix = css_frame_prefix(resource)
  
      # Check if custom.css already includes it. If so, let's remove it first
      exists = False
      if os.path.exists( custom ):
          with io.open(custom) as f:
              for line in f:
                  if line.find( prefix ) >= 0:
                      exists = True
                      break
      if exists:
          remove_custom_css( destdir, resource )
  
      # Fetch the CSS file
      cssfile += '.css'
      data = pkgutil.get_data( resource, os.path.join('resources',cssfile) )
      # get_data() delivers encoded data, str (Python2) or bytes (Python3)
  
      # Add the CSS at the beginning of custom.css
      # io.open uses unicode strings (unicode in Python2, str in Python3)
      with io.open(custom + '-new', 'wt', encoding='utf-8') as fout:
          fout.write( u'{}START ======================== */\n'.format(prefix))
          fout.write( data.decode('utf-8') )
          fout.write( u'{}END ======================== */\n'.format(prefix))
          if os.path.exists( custom ):
              with io.open( custom, 'rt', encoding='utf-8' ) as fin:
                  for line in fin:
                      fout.write( unicode(line) )
      os.rename( custom+'-new',custom)
docs: Add the kernel CSS to custom.css