[compat] Work around kwargs bugs in old 2.6 Python releases (Fixes #3813)

youtube_dl/compat.py

@@ -288,6 +288,14 @@ def compat_getpass(prompt, *args, **kwargs):
 else:
     compat_getpass = getpass.getpass
 
+# Old 2.6 and 2.7 releases require kwargs to be bytes
+try:
+    (lambda x: x)(**{'x': 0})
+except TypeError:
+    def compat_kwargs(kwargs):
+        return dict((bytes(k), v) for k, v in kwargs.items())
+else:
+    compat_kwargs = lambda kwargs: kwargs
 
 __all__ = [
     'compat_HTTPError',
@@ -299,6 +307,7 @@ def compat_getpass(prompt, *args, **kwargs):
     'compat_html_entities',
     'compat_html_parser',
     'compat_http_client',
+    'compat_kwargs',
     'compat_ord',
     'compat_parse_qs',
     'compat_print',

youtube_dl/options.py

@@ -8,6 +8,7 @@
 from .compat import (
     compat_expanduser,
     compat_getenv,
+    compat_kwargs,
 )
 from .utils import (
     get_term_width,
@@ -112,7 +113,7 @@ def _hide_login_info(opts):
         'conflict_handler': 'resolve',
     }
 
-    parser = optparse.OptionParser(**kw)
+    parser = optparse.OptionParser(**compat_kwargs(kw))
 
     general = optparse.OptionGroup(parser, 'General Options')
     general.add_option(