Support 308 Permanent Redirect HTTP redirect

[ingoogni]

Recognize raise cherrypy.HTTPRedirect('/new_uri', 308) as a legitimate redirect.

Refs:

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/308#Status
• https://tools.ietf.org/html/rfc7538#section-3
• https://airbrake.io/blog/http-errors/308-permanent-redirect
• https://stackoverflow.com/a/42138726/595220

What kind of change does this PR introduce?

• bug fix
• feature
• docs update
• tests/coverage improvement
• refactoring
• other

What is the related issue number (starting with #)

N/A

What is the current behavior? (You can also link to an open issue here)

raise cherrypy.HTTPRedirect('/new_uri', 308) is not recognized as a redirect and causes a ValueError

What is the new behavior (if this is a feature change)?

raise cherrypy.HTTPRedirect('/new_uri', 308) works the same way as other HTTP codes for redirection.

Other information:

N/A

Checklist:

• I think the code is well written
• I wrote good commit messages
• I have squashed related commits together after the changes have been approved
• Unit tests for the changes exist
• Integration tests for the changes exist (if applicable)
• I used the same coding conventions as the rest of the project
• The new code doesn't generate linter offenses
• Documentation reflects the changes
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences

[webknjaz]

Thanks for your contribution @ingoogni!

FTR I've just restarted a failed job on AppVeyor (and it's green now).
I'll probably need to improve the commit message before merging.

May I ask you to add a test case covering this change, please?

[webknjaz]

Should the default_status property be also updated?

[ingoogni]

Thank @webknjaz Regarding default_status, for what I found 308 is either implemented properly in browsers / clients or not at all. I wouldn't add 308 to the default_redirect. If 308 is not implemented the client should fall back on their unknown status procedure and just render the message.
I'll look into a test case.

[webknjaz]

Apparently, the status text is Permanent Redirect: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/308#Status

I've also checked the client behavior and found out that there's no user confirmation on the browser side so I've corrected that too.

[webknjaz]

Thanks @ingoogni!

[ingoogni]

Thanks @webknjaz