24: File based backends now reject non-string types for passwords.
2.3
===
21: Raise ValueError on blank username in plaintext keyring, unsupported in the storage format.
2.2
===
17: Drop dependency on keyring.py27compat and use six instead.
16: Minor tweaks to file-based backends.
2.1
===
Add persistent scheme and version tags for file based backends. Prepare for associated data handling in file based schemes.
2.0
===
12: Drop kwallet support, now superseded by the dual kwallet support in keyring.
1.3
===
9: Moved base file backend functionality from 'keyrings.alt.file' to 'keyrings.alt.base_file'. This allows the 'Windows' module to no longer trigger a circular import with the 'file' module.