[CI Problem] `python tests/scripts/ci.py lint` failed for not ignoring untracked files

[shingjan]

trafficstars

Repro:

# try to run linting locally on ubuntu
python tests/scripts/ci.py lint

Stack trace:

Linting the Python code with flake8...
+ tests/lint/flake8.sh
./_xxx/xxx.py:93:22: E999 SyntaxError: invalid syntax
    tvm.tir.transform.
                     ^
1     E999 SyntaxError: invalid syntax
1
+ cleanup
+ rm -rf '/tmp/1519064.*'
Error invoking Docker: Command failed: '/home/yj/tvm/docker/bash.sh -t --name ci-lint-auetm ci_lint bash .ci-py-scripts/ci-lint-auetm.sh'

in which ./_xxx/xx.py is actually an untracked file in this git repo.

cc: @areusch @driazati