flake8 >= 3.8.0 emits E741 ambiguous variable name 'l'

[Paride Legovini]

I couldn't find a relevant entry in the flake8 release notes [1], but flake8 3.7.9 does not emit the error, while 3.8.0 does. The fact that they were not being emitted was likely a flake8 bug, as the recommendation [2,3] causing the error is nothing new. The errors are:

./curtin/block/lvm.py:26:40: E741 ambiguous variable name 'l'
./curtin/block/__init__.py:1319:17: E741 ambiguous variable name 'l'
./curtin/block/bcache.py:322:31: E741 ambiguous variable name 'l'
./curtin/block/bcache.py:323:30: E741 ambiguous variable name 'l'
./tests/unittests/test_block_dasd.py:20:21: E741 ambiguous variable name 'l'
./tests/unittests/test_apt_source.py:961:26: E741 ambiguous variable name 'l'
./tests/vmtests/test_network.py:111:28: E741 ambiguous variable name 'l'
./tests/vmtests/test_fs_battery.py:168:27: E741 ambiguous variable name 'l'

I think renaming l to L would be enough, and won't require rewraps.

[1] https://flake8.pycqa.org/en/latest/release-notes/3.8.0.html
[2] https://www.python.org/dev/peps/pep-0008/#names-to-avoid
[3] https://www.flake8rules.com/rules/E741.html

[Paride Legovini (paride)]

Lucas' branch:

https://code.launchpad.net/~lamoura/curtin/+git/curtin/+merge/383811

[Paride Legovini (paride)]

I proposed another branch cherry-picking Ryan's commits (to get rid of the commits coming from the enable-kernel-crashdump branch) and pinning the flake8 version in the py3-flake8 environment.