_search_regex calls the sys.stderr.isatty() function for unix systems.
Py2exe uses a custom Stderr() stream which doesn't have an `isatty()`
function, leading to it's crash.
Fixes easily with checking that it's a unix system first.
Sadly applications using youtube-dl's python sources can't directly
access it's log stream. It's pretty much limited to stdout and stderr
only.
It should log to logging.Logger instance passed to YoutubeDL's params
dictionary.