What do these changes do?

Basically, avoid having a nocive fall back as the following one

try:
    resp = await req.json()
except ClieintResponseError:
    logging.warning("Invalid content-type")
    resp = loads(await req.read())

The ClieintResponseError can be raised by many reasons, and the case presented the fallback can be misleading having as a result twice ClieintResponseError because the source of the problem wasn't related to the content type.

With an ad-hoc exception, the client can code a more specific fallback case taking into account the differents source of problems with a cleaner interface, for example:

try:
    resp = await req.json()
except ContentTypeError:
    logging.warning("Invalid content-type by servcie ....")
    resp = loads(await req.read())
except ClieintResponseError:
    logging.exception("something went wrong")
    raise

Thanks to the current json() implementation once we have had a ContentTypeError exception is not possible to have a ClieintResponseError. Therefore, the developer can handle the errors as the previous example.

For backward compatibility the ContentTypeError inherits from ClieintResponseError.

Are there changes in behavior for the user?

No

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the changes folder
  • name it <issue_id>.<type> for example (588.bug)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."