[MERGE][#139318] bzr send @ win32: ensure that command line to invoking Thunderbird is 8-bit string, not unicode (because subprocess does not understand non-ascii unicode)

[Alexander Belchenko]

Aaron Bentley пишет:
> Alexander Belchenko wrote:
>> This patch fixes problem with UnicodeEncodeError and subprocess module @
>> win32.
> 
> According to my tests, both the encoded and unicode forms are allowed on
> Linux.  So we can encode on all platforms, which should give your change
> better test coverage.

Hm, I use encode(xx, 'replace') that will turn any character out of current
user encoding to '?'. If Linux accepts unicode in command-line, I think it's
better to not encode on Linux and therefore preserve actual subject line.