What Renovate type, platform and version are you using?

Hosted App

Describe the bug

black is a python code formatter that does not follow SemVer. Its version follows XX.YYbZ. Somehow, although it appears to follow PEP440, it's not handled by Renovate properly. It's not pulling the latest version.

Relevant debug logs

{
            "depName": "black",
            "currentValue": "==19.10b0",
            "datasource": "pypi",
            "fromVersion": "19.10b0",
            "depIndex": 0,
            "updates": [],
            "warnings": [],
            "sourceUrl": "https://github.com/psf/black",
            "changelogUrl": "https://github.com/psf/black/blob/master/CHANGES.md"
          },

To Reproduce
Please refer to the sample repository to replicate the issue.
https://github.com/alecgerona/unparsed-dependency-test