N5DatasetDiscoverer sometime throws errors if re-used.

[cmhulbert]

After creating an N5DatasetDiscoverer you can call discoverAndParseRecursive(base) where base is the base path inside the N5 container you want to start dataset discovery at. Typically, "/" or ""` are common.

Seemingly, it is not safe to call discvoerAndParseRecursive(base) multiple times on the same N5DatasetDiscoverer object. It is not a consistent failure, but sometimes an error occurs, which seems to originate in N5 deepList (specified in to saalfeldlab/n5#82). It doesn't seem to be an issue withdeepList but possibly some state that is incorrectly being retained from prior runs of discoverAndParseRecursive(base). For now, the solution is to create a new instance of N5DatasetDiscoverer when you want to discover, but it may be worth while investigating to see why the discoverer seems to (sometimes) not be safe to use this way.

The issues that brought this to the fore was an intermittent test failure resolved here: c6d0387