use @implementer instead of implements

[meejah]

Also, derive some more things from 'object'

[codecov-io]

Codecov Report

Merging #406 into master will decrease coverage by -0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #406      +/-   ##
==========================================
- Coverage   87.96%   87.95%   -0.02%     
==========================================
  Files         145      145              
  Lines       27439    27439              
  Branches     3805     3898      +93     
==========================================
- Hits        24138    24135       -3     
- Misses       2600     2602       +2     
- Partials      701      702       +1

Impacted Files	Coverage Δ
src/allmydata/immutable/repairer.py	100% <100%> (ø)	✅
src/allmydata/immutable/offloaded.py	92.85% <100%> (ø)	✅
src/allmydata/frontends/auth.py	59.59% <100%> (ø)	✅
src/allmydata/client.py	86.95% <100%> (ø)	✅
src/allmydata/monitor.py	100% <100%> (ø)	✅
src/allmydata/immutable/upload.py	96.34% <100%> (ø)	✅
src/allmydata/immutable/filenode.py	95.91% <100%> (ø)	✅
src/allmydata/dirnode.py	98.26% <100%> (ø)	✅
src/allmydata/web/directory.py	93.44% <100%> (ø)	✅
src/allmydata/frontends/sftpd.py	91.43% <100%> (ø)	✅
... and 33 more

---

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[warner]

Looks good. I see several classes that got updated to new-style.. that's good too. The only one that I think we can't update is HelperUploadResults, because it's also pb.Copyable, and foolscap doesn't handle new-style classes yet (despite them being around for ages).

Landing momentarily.

[warner]

Oh, I should have added a commit comment, but this also closes ticket 2636 (https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2636).