I'm not sure this is a problem with logging. The code immediately preceding the failure is:

    name = getattr(self.stream, 'name', '')
    if name:
        name += ' '

So, the failure occurs because the stream has a name attribute which is not a string. Even if sys.stderr itself is an unbuffered file, why is its 'name' attribute not a string? I don't imagine the name would be actually used for I/O, and having it set to an integer is a surprise.

I propose to close this (and the associated PR) unless a good reason is given why we have to support non-string names here.