This adds Node._create_tub(), which knows how to make a Tub with all the
right options and connection handlers that were specified in
tahoe.cfg (the connection handlers are disabled for now, but they'll get
implemented soon).
The new Node.create_main_tub() calls it. This main Tub is used:
* to connect to the Introducer
* to host the Helper (if enabled)
* to host the Storage Server (if enabled)
Node._create_tub() is also passed into the StorageFarmBroker, which
passes it into each NativeStorageServer, to create the (separate) Tub
for each server connection. _create_tub knows about the options, and
NativeStorageServer can override the connection handlers. This way we
don't need to pass tub options or default handlers into Client,
StorageFarmBroker, or NativeStorageServer.
A number of tests create NativeStorageServer objects: these were updated
to match the new arguments. test_storage_client was simplified because
we no longer need to mock out the Tub() constructor.
A minimally-defined static server only specifies server_id,
anonymous-storage-FURL, and permutation-seed-base32. But the WUI Welcome
page wouldn't render (it raised an exception) without also defining
nickname and version. This allows those values to be missing.
This doesn't reveal very much information, but does tell
you if magic-folder is currently working and if not it will
indicate when the last attempt to do a remote scan was.
Improve error-handling for directories if you ask for JSON from
the /uri endpoint, but an error occurs (you get a proper HTTP
status code and a valid JSON object).
For 'tahoe magic-folder status' e now retrieve *all* the remote data
required in the CLI before doing anything else so that errors can be
shown immediately. Use the improved JSON endpoints to print better
errors.
