support parsing pylint output

This parses pylint output with a simple regexp and counts one failure per
message reported.

This has not been tested yet, but we decided to apply this commit already.

/acked-by @kirr
/reviewed-on nexedi/nxdtest!11
3 jobs for <span class="ref-name">feat/pylint</span> in 0 seconds
Status Job ID Name Coverage
  External
passed nxdtest.UnitTest-Master.Python2.WIP

00:00:29

passed nxdtest.UnitTest-Master.Python3.WIP

passed nxdtest.UnitTest-Master.Python3.WIP

00:01:06