Flake errors

Running flake locally gives

```
E:\code\emsdk\emscripten\master>flake8
.\emcc.py:2092:23: E741 ambiguous variable name 'l'
.\tests\test_core.py:3040:24: E741 ambiguous variable name 'l'
.\tests\test_core.py:3041:29: E741 ambiguous variable name 'l'
.\tests\test_core.py:4815:30: E741 ambiguous variable name 'l'
.\tests\test_other.py:532:5: E124 closing bracket does not match visual indentation
.\tests\test_other.py:1900:25: E741 ambiguous variable name 'l'
.\tests\test_other.py:2150:22: E741 ambiguous variable name 'l'
.\tools\building.py:85:21: E741 ambiguous variable name 'l'
.\tools\shared.py:637:27: E741 ambiguous variable name 'l'
.\tools\shared.py:645:28: E741 ambiguous variable name 'l'
.\tools\system_libs.py:1621:22: E741 ambiguous variable name 'l'
.\tools\update_symbols.py:55:27: E741 ambiguous variable name 'l'
.\tools\update_symbols.py:56:18: E741 ambiguous variable name 'l'
.\tools\update_symbols.py:59:33: E741 ambiguous variable name 'l'

E:\code\emsdk\emscripten\master>flake8 --version
3.8.4 (mccabe: 0.6.1, pycodestyle: 2.6.0, pyflakes: 2.2.0) CPython 3.8.1 on Windows
```

I wonder how that does not(?) happen on the CI - maybe a version difference?