(🐞) crash with `--pretty` from attrs raising an error in the wrong file

> git clone https://github.com/DataDog/dd-trace-py
> cd dd-trace-py
> pip install -e .
> pip install mypy
> mypy --strict --check-untyped-defs | grep threading.py
ddtrace/profiling/collector/threading.py:25: error: Need type annotation for "recorder"  [var-annotated]
ddtrace/profiling/collector/threading.py:29: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
ddtrace/profiling/collector/threading.py:316: error: Need type annotation for "tracer"  [var-annotated]
> mypy --strict --check-untyped-defs --pretty
...
  File "mypy/main.py", line 100, in main
  File "mypy/main.py", line 182, in run_build
  File "mypy/build.py", line 192, in build
  File "mypy/build.py", line 266, in _build
  File "mypy/build.py", line 2942, in dispatch
  File "mypy/build.py", line 3340, in process_graph
  File "mypy/build.py", line 3465, in process_stale_scc
  File "mypy/errors.py", line 915, in file_messages
  File "mypy/errors.py", line 885, in format_messages
IndexError: list index out of range

threading.py:316: error, threading only has 43 lines in it.

按照 issue 中的设置命令操作后，使用 mypy --strict --check-untyped-defs --pretty 重现崩溃。从 mypy/errors.py 开始，重点查看 format_messages 和 file_messages，并将报告的位置与 ddtrace/profiling/collector/threading.py 中的错误进行比较；当 --pretty 在没有 IndexError 的情况下完成，并报告有效位置时，即表示完成。