Yields the body of the buffered file.

def body(self):
        """Yields the body of the buffered file."""
        for fp, need_close in self.files:
            try:
                name = os.path.basename(fp.name)
            except AttributeError:
                name = ''
            for chunk in self.gen_chunks(self.envelope.file_open(name)):
                yield chunk
            for chunk in self.file_chunks(fp):
                yield chunk
            for chunk in self.gen_chunks(self.envelope.file_close()):
                yield chunk
            if need_close:
                fp.close()
        for chunk in self.close():
            yield chunk