Support pylint 2.2.2

[nth10sd]

This enables us to run pylint on Python 3.7 in Travis.

[codecov-io]

Codecov Report

Merging #218 into master will decrease coverage by <.01%.
The diff coverage is 39.21%.

@@            Coverage Diff             @@
##           master     #218      +/-   ##
==========================================
- Coverage   44.48%   44.48%   -0.01%     
==========================================
  Files          39       39              
  Lines        2740     2736       -4     
==========================================
- Hits         1219     1217       -2     
+ Misses       1521     1519       -2

Impacted Files	Coverage Δ
tests/js/test_build_options.py	94.73% <0%> (ø)	⬆️
src/funfuzz/util/lithium_helpers.py	13.15% <0%> (ø)	⬆️
src/funfuzz/util/os_ops.py	17.12% <0%> (ø)	⬆️
src/funfuzz/util/sm_compile_helpers.py	72.83% <0%> (ø)	⬆️
src/funfuzz/util/fork_join.py	26.47% <0%> (ø)	⬆️
src/funfuzz/util/create_collector.py	30% <0%> (ø)	⬆️
src/funfuzz/util/repos_update.py	25% <0%> (ø)	⬆️
src/funfuzz/util/hg_helpers.py	41.48% <0%> (ø)	⬆️
src/funfuzz/util/s3cache.py	52.63% <100%> (ø)	⬆️
src/funfuzz/bot.py	20.74% <100%> (ø)	⬆️
... and 9 more

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