Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Pull request

v2:
 * Replaced "Launchpad:" tag with "Buglink:" as documented on the SubmitAPatch wiki page [Philippe]

# gpg: Signature made Tue 15 Oct 2019 09:49:05 BST
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/tracing-pull-request:
  trace: avoid "is" with a literal Python 3.8 warnings
  trace: add --group=all to tracing.txt

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>