testing: explicitly set response content type header to html

[mister-roboto]

@perrinjerome you need to sign the Plone Contributor Agreement in order to merge this pull request.

Learn about the Plone Contributor Agreement: http://docs.plone.org/develop/coredev/docs/contributors_agreement_explained.html

[mister-roboto]

@perrinjerome thanks for creating this Pull Request and helping to improve Plone!

TL;DR: Finish pushing changes, pass all other checks, then paste a comment:

@jenkins-plone-org please run jobs

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass, but it takes 30-60 min. Other CI checks are usually much faster and the Plone Jenkins resources are limited, so when done pushing changes and all other checks pass either start all Jenkins PR jobs yourself, or simply add the comment above in this PR to start all the jobs automatically.

Happy hacking!

[perrinjerome]

BTW, there's something strange in https://plone.org/foundation/about/materials/foundation-resolutions/patch-policy-052011

[perrinjerome]

This is an early follow up for https://github.com/zopefoundation/Zope/pull/1075

This falls in

Changes required by changes in other modules that introduce no new logic.

category, so I guess contributor agreement will not be needed

[mauritsvanrees]

Why did this not work? Trying again:

@jenkins-plone-org please run jobs

Might be because mr.roboto cannot handle the fork of the repo.

[mauritsvanrees]

All tests pass, except two unrelated robot tests on 5.2. I merge. Thanks!

[perrinjerome]

Thank you very much @mauritsvanrees for reviewing the patches, trying them on CI and also accepting that this was OK as an exception to the contributor agreement. I probably don't have a problem with this agreement, but this would need to be validated by my employer. This is probably OK as well, but I was lazy of going through the paperwork. Thanks again.