Pylint output html-escapes entities

[jgsogo]

Changelog: omit
Docs: omit

With the new version of Pylint (2.3.0), the JSON output contains escaped characters:

[
    {
        "type": "convention",
        "module": "conanfile",
        "obj": "TestConan.build",
        "line": 9,
        "column": 15,
        "path": "conanfile.py",
        "symbol": "invalid-name",
        "message": "Variable name "v" doesn't conform to snake_case naming style",
        "message-id": "C0103"
    }
]

I've opened an issue in their repo (pylint-dev/pylint#2769), and also I'm providing here a patch.

[jgsogo]

Closing this one, let's wait for the next pylint version (if they consider this behavior a regression or not).