[utils] update_url_query: Encode the strings in the query dict

The test case with {'test': '第二行тест'} was failing on python 2 (the non-ascii characters were replaced with '?').

youtube_dl/utils.py

@@ -1743,6 +1743,7 @@ def update_url_query(url, query):
     parsed_url = compat_urlparse.urlparse(url)
     qs = compat_parse_qs(parsed_url.query)
     qs.update(query)
+    qs = encode_dict(qs)
     return compat_urlparse.urlunparse(parsed_url._replace(
         query=compat_urllib_parse.urlencode(qs, True)))