Repair colorama wrapping on non-Windows platforms (#1670)

* Repair colorama wrapping on non-Windows platforms

The wrap_stream_for_windows() function calls
colorama.initialise.wrap_stream() function to apply colorama's magic to
wrapper to the output stream. Except this wrapper is only applied on
Windows platforms that need it, otherwise the original stream is
returned as-is.

The colorama wrapped stream lacks a detach() method, so a no-op lambda
was being assigned to the wrapped stream.

The problem is that the no-op lambda was being assigned unconditionally
whether or not colorama actually returns a wrapped stream, thus
replacing the original TextIOWrapper's detach() method. Replacing the
detach() method with a no-op lambda is the root cause of the problem
observed in #1664.

The solution is to only assign the no-op detach() method if the stream
lacks its own detach() method.

Repairs #1664