Use find_packages

[exarkun]

It is a shorter and more reliably way to provide a value for the packages parameter.

Fixes https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2897

[warner]

#434 is fixed.. wanna rebase and re-push this? I think it should pass CI this time.

[codecov-io]

Codecov Report

Merging #433 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #433      +/-   ##
=========================================
- Coverage   88.02%     88%   -0.03%     
=========================================
  Files         147     147              
  Lines       27835   27835              
  Branches     3973    3973              
=========================================
- Hits        24501   24495       -6     
- Misses       2619    2624       +5     
- Partials      715     716       +1

Impacted Files	Coverage Δ
src/allmydata/mutable/publish.py	95.65% <0%> (-1.02%)	⬇️
src/allmydata/web/status.py	82.86% <0%> (+0.11%)	⬆️

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[warner]

the coverage issue is unrelated, I'll try to fix that later

+1, will land soon