docs: def setuptools_install_options(local_storage_folder):
      """
      Return options to make setuptools use installations from the given folder.
  
      No other installation source is allowed.
  
      """
      if local_storage_folder is None:
          return []
      # setuptools expects its find-links parameter to contain a list of link
      # sources (either local paths, file: URLs pointing to folders or URLs
      # pointing to a file containing HTML links) separated by spaces. That means
      # that, when specifying such items, whether local paths or URLs, they must
      # not contain spaces. The problem can be worked around by using a local
      # file URL, since URLs can contain space characters encoded as '%20' (for
      # more detailed information see below).
      #
      # Any URL referencing a folder needs to be specified with a trailing '/'
      # character in order for setuptools to correctly recognize it as a folder.
      #
      # All this has been tested using Python 2.4.3/2.4.4 & setuptools 1.4/1.4.2
      # as well as Python 3.4 & setuptools 3.3.
      #
      # Supporting paths with spaces - method 1:
      # ----------------------------------------
      # One way would be to prepare a link file and pass an URL referring to that
      # link file. The link file needs to contain a list of HTML link tags
      # (<a href="..."/>), one for every item stored inside the local storage
      # folder. If a link file references a folder whose name matches the desired
      # requirement name, it will be searched recursively (as described in method
      # 2 below).
      #
      # Note that in order for setuptools to recognize a local link file URL
      # correctly, the file needs to be named with the '.html' extension. That
      # will cause the underlying urllib2.open() operation to return the link
      # file's content type as 'text/html' which is required for setuptools to
      # recognize a valid link file.
      #
      # Supporting paths with spaces - method 2:
      # ----------------------------------------
      # Another possible way is to use an URL referring to the local storage
      # folder directly. This will cause setuptools to prepare and use a link
      # file internally - with its content read from a 'index.html' file located
      # in the given local storage folder, if it exists, or constructed so it
      # contains HTML links to all top-level local storage folder items, as
      # described for method 1 above.
      if " " in local_storage_folder:
          find_links_param = utility.path_to_URL(local_storage_folder)
          if find_links_param[-1] != "/":
              find_links_param += "/"
      else:
          find_links_param = local_storage_folder
      return ["-f", find_links_param, "--allow-hosts=None"]