A TextIOWrapper that wraps _winconsole._WindowsConsoleWriter expects …

…a buffered stream.

TextIOWrapper expects a *buffered* stream not an unbuffered one. It wont
check how much data was written and will drop data if you don't write it
all.

This reproduces quite well on Python 3.6. Likely due to changes in
TextIOWrapper.

Fixes: #816

click/_winconsole.py

@@ -210,14 +210,14 @@ def _get_text_stdin(buffer_stream):
 
 def _get_text_stdout(buffer_stream):
     text_stream = _NonClosingTextIOWrapper(
-        _WindowsConsoleWriter(STDOUT_HANDLE),
+        io.BufferedWriter(_WindowsConsoleWriter(STDOUT_HANDLE)),
         'utf-16-le', 'strict', line_buffering=True)
     return ConsoleStream(text_stream, buffer_stream)
 
 
 def _get_text_stderr(buffer_stream):
     text_stream = _NonClosingTextIOWrapper(
-        _WindowsConsoleWriter(STDERR_HANDLE),
+        io.BufferedWriter(_WindowsConsoleWriter(STDERR_HANDLE)),
         'utf-16-le', 'strict', line_buffering=True)
     return ConsoleStream(text_stream, buffer_stream)