Follow-up to #9199: Fix str.join use, add newlines.

Thanks to Konrad Delong for writing a test for upload_docs
--show-response in distutils2, letting me catch my mistake.

command/upload.py

@@ -194,5 +194,5 @@ class upload(PyPIRCCommand):
             self.announce('Upload failed (%s): %s' % (r.status, r.reason),
                           log.ERROR)
         if self.show_response:
-            msg = ''.join('-' * 75, r.read(), '-' * 75)
+            msg = '\n'.join(('-' * 75, r.read(), '-' * 75))
             self.announce(msg, log.INFO)