fix #116

`getpass.getpass` only accepts `str` as its first parameter on Windows.

Author: mhils

twine/utils.py

@@ -122,6 +122,6 @@ def get_userpass_value(cli_value, config, key, prompt_strategy):
     get_userpass_value,
     key='password',
     prompt_strategy=functools.partial(
-        getpass.getpass, 'Enter your password: ',
+        getpass.getpass, b'Enter your password: ',
     ),
 )