pylint-27 failed but not caught in Pre/PostCommit

14:54:25 Running isort for module apache_beam  gen_protos.py  setup.py  test_config.py:
14:54:31 ERROR: /home/jenkins/jenkins-slave/workspace/beam_PostCommit_Python_Verify_PR/src/sdks/python/apache_beam/runners/portability/stager.py Imports are incorrectly sorted.
14:54:31 --- /home/jenkins/jenkins-slave/workspace/beam_PostCommit_Python_Verify_PR/src/sdks/python/apache_beam/runners/portability/stager.py:before	2018-11-08 21:49:32.444622
14:54:31 +++ /home/jenkins/jenkins-slave/workspace/beam_PostCommit_Python_Verify_PR/src/sdks/python/apache_beam/runners/portability/stager.py:after	2018-11-08 22:54:29.293067
14:54:31 @@ -60,9 +60,9 @@
14:54:31  from apache_beam.io.filesystems import FileSystems
14:54:31  from apache_beam.options.pipeline_options import SetupOptions
14:54:31  from apache_beam.options.pipeline_options import WorkerOptions
14:54:31 -from apache_beam.runners.internal import names
14:54:31  # TODO(angoenka): Remove reference to dataflow internal names
14:54:31  from apache_beam.runners.dataflow.internal.names import DATAFLOW_SDK_TARBALL_FILE
14:54:31 +from apache_beam.runners.internal import names
14:54:31  from apache_beam.utils import processes
14:54:31  
14:54:31  # All constants are for internal use only; no backwards-compatibility
14:54:31 Command exited with non-zero status 1
14:54:31 418.43user 9.73system 1:03.13elapsed 678%CPU (0avgtext+0avgdata 326144maxresident)k
14:54:31 0inputs+208outputs (0major+862242minor)pagefaults 0swaps
14:54:31 ERROR: InvocationError for command '/usr/bin/time /home/jenkins/jenkins-slave/workspace/beam_PostCommit_Python_Verify_PR/src/sdks/python/scripts/run_pylint.sh' (exited with code 1)
14:54:31 ___________________________________ summary ____________________________________
14:54:31 ERROR:   py27-lint: commands failed
14:54:31 # Retry once for the specific exit code -11.
14:54:31 if [[ $? == -11 ]]; then
14:54:31   tox -c tox.ini --recreate -e $1
14:54:31 fi
14:54:31 :beam-sdks-python:lintPy27 (Thread[Daemon worker,5,main]) completed. Took 1 mins 21.549 secs.