Update raven to 6.0.0

[pyup-bot]

There's a new version of raven available.
You are currently using 5.32.0. I have updated it to 6.0.0

These links might come in handy: PyPI | Changelog | Repo

Changelog

6.0.0

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• Strip whitespace from DSNs automatically.
• Add last_event_id accessor to Client.
• Do not require sys.argv to be available any more.
• Tags defined on a logging handler will now be merged with individual log record's tags.
• Added explicit support for multidicts in the django client.
• Refactored transports to support multiple URLs. This might affect
  you if you have custom subclasses of those. The main change is that
  the URL parameter moved from the constructor into the send method.
• Corrected an issue with recursive route resolvers which commonly
  affected things like django-tastyepie.
• Corrected an issue where Django's HTTP request was not always available
  within events.

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖