flake8 checks not enforced

[leezu]

CI currently runs flake8 on every run

dmlc-core/.travis.yml

Lines 67 to 71 in c8f7f9c

	before_script:
	# stop the build if there are Python syntax errors or undefined names
	- flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics
	# exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
	- flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics

Exit code is set to 0 thus flake8 not enforced.
Likely nobody will check the CI log for warnings and the check is thus superfluous.

Example run: https://travis-ci.org/dmlc/dmlc-core/jobs/657898840?utm_medium=notification&utm_source=github_status