Explicitly set max-line-length

Author: wenbinf

tox.ini

@@ -39,5 +39,5 @@ skip_install = true
 description = run static analysis and style check using flake8
 basepython = python3.8
 deps = flake8
-commands = python -m flake8 --show-source listennotes tests setup.py
+commands = python -m flake8 --show-source listennotes tests setup.py --max-line-length=100
 skip_install = true