changing base image for unit tests

2 jobs for impelemtation_preprocessing in 3 minutes and 1 second (queued for 1 second)
Name Stage Failure
failed
linter Test
Collecting pyflakes<2.2.0,>=2.1.0
Downloading pyflakes-2.1.1-py2.py3-none-any.whl (59 kB)
Installing collected packages: entrypoints, pycodestyle, mccabe, pyflakes, flake8
Successfully installed entrypoints-0.3 flake8-3.7.9 mccabe-0.6.1 pycodestyle-2.5.0 pyflakes-2.1.1
$ flake8 ./umami
./umami/preprocessing.py:85:80: E501 line too long (80 > 79 characters)
./umami/preprocessing.py:87:80: E501 line too long (80 > 79 characters)
./umami/preprocessing.py:89:80: E501 line too long (80 > 79 characters)
ERROR: Job failed: exit code 1