Hmm, are Notice, User-notice, Developer-notice, and Sysadmin-notice not sufficient? If not, do you plan to "copy" their workflow or how will creating such a tag help exactly?

The pywikibot userbase doesnt neatly overlap with those. e.g. When pywikibot devs are planning a breaking change, say for example the switch from using library httplib2 to requests (the last big breaking change, and it caused quite a mess), it isnt relevant to Wikimedia editors, so User-notice isnt appropriate according to the definition of that tag. However it effects pywikibot users, which is usually only a few people per wiki, some of which are sysadmins , some are developers, but those tags are not relevant either according to the definition of them. The sysadmin tag is probably the closest match, but it is only relevant for some of our announcements. e.g. if we break the APISite.upload method API slightly (which is currently being considered), sysadmins and the typical prepackaged script user doesnt care, but anyone using that method in custom code may need to make slight alterations.

I havent looked closely at the workflows the existing tags use, however roughly what I have in mind is three columns:

1. concept work / early developments that may need to be announced
2. code about to be merged which does need to be announced, possibly with multiple announcements depending on the scale of the change
3. a 'Done' column for when the announcements have hit the audience sufficiently that most users have been effectively warned about the change.

Announcements would go out on the pywikibot-announce list, and/or possibly a MassMessage for the specific users who subscribe to these announcements. I dont believe we've got the capacity to manage a newsletter, or even work closely with the TechNews team except for very large breakages that impact wiki processes (e.g. T101214: Decommission compat kills processes in production on wikis, in turn impacting users who've never opened a text editor in their life).

So if anybody can provide a project description (plus maybe who is supposed to add this tag to tasks?) I'm happy to create this project in Phabricator.
See https://www.mediawiki.org/wiki/Phabricator/Creating_and_renaming_projects#Guidelines

"pywikibot-announce is for tasks that will have an impact on users of Pywikibot. It should be added by developers whenever a sizeable impact is under development.
It isnt expected that users will need to watch this project; instead notices will be sent out to users once the code is merge, or in advance of code merge for large impact changes."
?

@jayvdb Is this tag still needed? Then I will create it for you.

@Luke081515 , I believe a tag will be useful.