assert [1] is a Python keyword hence Flake8 raised an error:
"E275 missing whitespace after keyword" [2].

[1] https://docs.python.org/3/reference/lexical_analysis.html#keywords
[2] https://www.flake8rules.com/rules/E275.html

Change-Id: I76bbe10b850c38a3fbb38c4a2f5ee17ca5b91b4e