tests: force \n newlines when writing to sys.stdout
Without this, Python 3 on Windows inserts some \r that aren't
present in the input, causing test-http-bad-server.t to fail.
After this change, the test passes on Python 3 on Windows!
Differential Revision: https://phab.mercurial-scm.org/D8341
public attribute not declared in interfaces: badpeer.badattribute
public attribute not declared in interfaces: badpeer.badmethod