open errors in quickfix

1. in Vim, run command :cexpr system('command that returns quickfix format')
2. in Terminal, vim -q <(command that returns quickfix error format)

Example for quickfix format

./lambdas/atr_notification/__init__.py:1:1: F401 'json' imported but unused
./lambdas/atr_notification/__init__.py:2:1: F401 'boto3' imported but unused
./lambdas/atr_notification/__init__.py:4:1: F401 'lambdas.common.config.oneview.SNS_TARGET_ARN' imported but unused