Logging fails with dictionary keys that are bytes

[itamarst]

On Python 2, JSON would happily encode byte strings, so long as they were ASCII at least. In Python, the json module knows nothing about bytes.

In Tahoe-LAFS, there is now custom code to deal with this, e.g. https://github.com/tahoe-lafs/tahoe-lafs/blob/master/src/allmydata/util/jsonbytes.py#L31 and later parts of that module.

Foolscap is still lacking this infrastructure. As such, when a log message comes in where keys are bytes, it fails, e.g.:

2021-05-10T10:40:57-0400 [stdout#info] GATHERER: unable to serialize {'facility': 'tahoe.storage_broker', 'format': '%(name)s provided version info %(version)s', 'incarnation': ('86433dff70db2783', None), 'level': 10, 'name': b'q26hhekw', 'num': 626, 'parent': 617, 'time': 1620657650.2063904, 'umid': 'SWmJYg', 'version': {b'application-version': b'tahoe-lafs/1.14.0.post3323', b'http://allmydata.org/tahoe/protocols/storage/v1': {b'available-space': 7235896832, b'delete-mutable-shares-with-zero-length-writev': True, b'fills-holes-with-zero-bytes': True, b'maximum-immutable-share-size': 7235896832, b'maximum-mutable-share-size': 69105000000000000, b'prevents-read-past-end-of-share-data': True, b'tolerates-immutable-read-overrun': True}}}: keys must be a string}