I've been seeing inconsistent results for 'RepositoryTests.test_password_decryption_failed`, which tests that we don't crash when the `SECRET_KEY` has been mistakenly changed and stored passwords cannot be decrypted. While this works *most* of the time by properly catching the decode error, occasionally the random IV used during AES-CFB causes the decoded result to be valid(ish) unicode. These almost always result in unprintable characters, however. This change adds a step to `decrypt_password` to check if the result is printable, and if not, raise a `ValueError`. This should make it so this test (and handling of the situation in production) is much more reliable. Testing Done: Ran unit tests.