Put max-line-length of 120 in pycodestyle config, rather than completely disabling E501.

.gitlab-ci.yml

@@ -22,5 +22,5 @@ codestyle:
   - apt-get install -y --no-install-recommends python3-dev python3-pip python3-coverage python3-setuptools build-essential
   - pip3 install wheel pycodestyle mypy
   - pip3 install -r requirements.txt
-  - pycodestyle --ignore=E501 matemat
+  - pycodestyle matemat
   - mypy --ignore-missing-imports --strict -p matemat

setup.cfg

@@ -0,0 +1,3 @@
+[pycodestyle]
+max-line-length = 120
+statistics = True