Updated: Comment #9
Guzzle development was very active since we last updated, the most important change for us right now is a fix that allows us to deal with(critical bug).
Less urgent but very important in the long-term is that we need a version of Guzzle that is going to be supported long enough for us.
The downside is that this introduces a number of BC breaks, see comment #5 for the detailed explanation and interdiff for the changes that affect our current usage.
Update to the latest stable 3.7.* version. @mtdowling, the Guzzle maintainer, confirmed in #3 that 3.7 is the much better version to lock into and that he can support it as a LTS release (although it has yet to be defined what that exactly means).
Get an OK from a core maintainer about the API change. Possibly define with the security team how long this needs to be supported (Necessary anyway, also for other vendor-code, so can be a separate issue).
User interface changes
See comment #5 and Guzzle's upgrading documentation.
Original report by Yaron Tal
In order to solvewe need to update Guzzle. I think the impact of this might be, quite big, so if someone with more knowledge of this could jump in?
The patch for Guzzle that solves our problem:
The oldest release which includes this patch is 3.6.0. We currently use 3.1.* according to the composer.json in the Drupal root.
PASSED: [[SimpleTest]]: [MySQL] 57,951 pass(es). View
FAILED: [[SimpleTest]]: [MySQL] 57,621 pass(es), 2 fail(s), and 1 exception(s). View