Upgrade CherryPy to 13.0.1 after namespacing issue was resolved

[benjaoming]

Summary

Back on track with upstream CherryPy after namespaced packages has temporarily been accepted as a blocker.

Will have to work on pip install <...> -t <...> to resolve how we avoid similar errors in the future. Possibly upstream.

Reviewer guidance

None, I think we're safe -- will give it a manual test spin.

References

#2972
cherrypy/cherrypy#1671

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Contributor Checklist

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• Contributor has fully tested the PR manually
• Screenshots of any front-end changes are in the PR description
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')

Reviewer Checklist

• Automated test coverage is satisfactory
• Reviewer has fully tested the PR manually
• PR has been tested for accessibility regressions
• External dependencies files were updated (yarn and pip)
• Documentation is updated
• Link to diff of internal dependency change is included
• CHANGELOG.rst is updated for high-level changes
• Contributor is in AUTHORS.rst

[codecov]

Codecov Report

Merging #2976 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #2976   +/-   ##
========================================
  Coverage    76.09%   76.09%           
========================================
  Files          187      187           
  Lines         7283     7283           
  Branches       915      915           
========================================
  Hits          5542     5542           
  Misses        1562     1562           
  Partials       179      179

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[lyw07]

Tested on Ubuntu 14.04, 16.04, 17.10 and Mac OS X. Looks good to me!