lint failed while running “make presubmit”

when I run `make presubmit`or `make lint` ,there is always be a lint failed.

`make lint`

```
source .venv/bin/activate && python3 presubmit.py lint
************* Module presubmit
```

then the error occurs

```
Your code has been rated at 9.95/10 (previous run: 9.95/10, +0.00)
ERROR: lint failed, see errors above.
Failed.
Makefile:69: recipe for target 'lint' failed
make: *** [lint] Error 1
```

but there is some differences between this error and #555
in the information printed by pylint ,there is no E reported but only R
and I debugged `presubmit.py` with Pycharm . It shows value of `returncode = subprocess.run(command, check=False).returncode` is 8
and I can't find what this value means in python official documents.
My python version is 3.7.5
My system version is Ubuntu 18.04 LTS