def abspath_to_urlpath(path, base, os_sep=os.sep):
return relativize_path(path, base, os_sep).replace(os_sep, '<STR_LIT:/>')<EOL>
Make filesystem absolute path uri relative using given absolute base path.

:param path: absolute path
:param base: absolute base path
:param os_sep: path component separator, defaults to current OS separator
:return: relative uri
:rtype: str or unicode
:raises OutsideDirectoryBase: if resulting path is not below base