Fix some `pylint -E` errors

Fixed all apart from:

```
************* Module letsencrypt.client.apache_configurator
E:753,24: Class 'value' has no 'partition' member (no-member)
E:754,22: Class 'value' has no 'partition' member (no-member)
************* Module letsencrypt.client.recovery_token_challenge
E: 19,29: Module 'dialog' has no 'generic_input' member (no-member)
************* Module letsencrypt.client.client
E:570,47: Instance of 'str' has no 'file' member (but some types could not be inferred) (maybe-no-member)
```