[AIRFLOW-4661] Make airflow/config_templates Pylint compatible

[arkadiuszbach]

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[turbaszek]

@mik-laj what do you think about the error? Does it look like a flaky test?
https://travis-ci.org/apache/airflow/builds/596117901

[mik-laj]

I restarted build.

[codecov-io]

Codecov Report

Merging #6300 into master will decrease coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #6300      +/-   ##
==========================================
- Coverage   80.41%   80.38%   -0.03%     
==========================================
  Files         612      612              
  Lines       35473    35474       +1     
==========================================
- Hits        28525    28517       -8     
- Misses       6948     6957       +9

Impacted Files	Coverage Δ
airflow/config_templates/airflow_local_settings.py	80.48% <100%> (+0.48%)	⬆️
airflow/jobs/local_task_job.py	85% <0%> (-5%)	⬇️
airflow/models/taskinstance.py	93.26% <0%> (-0.51%)	⬇️
airflow/utils/dag_processing.py	56.55% <0%> (-0.35%)	⬇️

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