Assert result string in test_prompt_for_authentication

Author: deveshks

tests/functional/test_install_config.py

@@ -243,7 +243,8 @@ def test_prompt_for_authentication(script, data, cert_factory):
                             "--cert", cert_path, "--client-cert", cert_path,
                             'simple', expect_error=True)
     print(result)
-    assert 'User for {}:{}'.format(server.host, server.port) in result.stdout
+    assert 'User for {}:{}'.format(server.host, server.port) in \
+           result.stdout, str(result)
 
 
 def test_do_not_prompt_for_authentication(script, data, cert_factory):