Python < 2.7.9 does not have the ssl.SSLContext attribute.
ssl.SSLContext is only required when we want to validate the SSL
connection. If `validate_certs` is false, we don't initialize the
`ssl_context` variable.
Add unit-test coverage and a little refactoring:
- avoid the use of `mocker`, when we can push `monkeypatch` which is
`pytest`'s default.
- use `mock.Mocker()` when possible
closes: #57072
