Separate output tool error and mypy warnings (stderr, stdout, file)

Today I run mypy > mypy.report to let jenkins parse the output log and present it. However then mypy crashes and prints errors, those also go on stdout and into my report file. It would be nice with some way of separating the output.

example on tool error:

$ mypy --no-incremental --disable-error-code import --follow-imports skip . > mypy.report
 Duplicate module named "benchmark" (also at "a/b/1/benchmark.py")
 a/b/2/benchmark.py: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#mapping-file-paths-to-modules for more info
 a/b/2/benchmark.py: note: Common resolutions include: a) using `--exclude` to avoid checking one of them, b) adding `__init__.py` somewhere, c) using `--explicit-package-bases` or adjusting MYPYPATH

Suggestion:

1. Could these errors be printed to stderr? Should there in that case be an option to do so?
2. option flag to set output_file for the report, but still output errors to stdout.

Empieza rastreando el manejo actual de mypy en la línea de comandos de los errores de las herramientas y de la salida de informes. Compara los dos comportamientos solicitados —enviar los errores de las herramientas a stderr o configurar un archivo de informe conservando stdout— y define qué interfaz debe implementarse; la tarea estará terminada cuando Jenkins pueda separar de forma fiable los errores del informe.