Support for reporting problems to file with machine-readable format

[fenuks]

It would be great to be able to output problems to some machine-readable format for further processing (in addition to human-readable terminal output). In my example, I would like add pydoclint to GitLab CI job, and GitLab can load CodeClimate report as job output.

Currently one has to write own parser and converter for terminal output, that probably is not guaranteed to be stable.