UnicodeEncodeError: 'ascii' codec can't encode character u'\xa0' in position 23: ordinal not in range(128)

Hello,
I have a similar problems in the “Serial Monitor”. And also the message below:

bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)

Indeed there is no en_US.UTF-8 locale on my system, the default is fr_FR.UTF-8.
I have generated en_US.UTF-8 and the problem seems to be gone for now.

The workaround is easy, but why is en_US.UTF-8 hardcoded somewhere?

Thanks a lot for a great tool