[BEAM-1964] Fix lint issues for linter upgrade - part 1/?

[sb2nov]

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R: @aaltay PTAL

[aaltay]

LGTM

[coveralls]

Coverage decreased (-0.003%) to 70.441% when pulling 78a2af1 on sb2nov:BEAM-1964-upgrade-pylint-1 into 8761d86 on apache:master.

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Java_MavenInstall/9512/
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