[CI] add flake8 test

5 jobs for integrate_ewoks_v2 in 8 seconds (queued for 5 seconds)
Name Stage Failure
check_style Style
Installing collected packages: pyflakes, pycodestyle, zipp, typing-extensions, importlib-metadata, mccabe, flake8
Successfully installed flake8-3.9.2 importlib-metadata-4.8.1 mccabe-0.6.1 pycodestyle-2.7.0 pyflakes-2.3.1 typing-extensions- zipp-3.6.0
WARNING: You are using pip version 19.2.3, however version 21.2.4 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
$ flake8 est
$ flake8 orangecontrib
orangecontrib/est/widgets/utils/noise.py:196:24: F821 undefined name 'ProcessRunnable'
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1