From mw core

	"badaccess-groups": "The action you have requested is limited to users in {{PLURAL:$2|the group|one of the groups}}: $1.",

And then in ContentTranslation...

				if ( $campaign ) {
					// Show login page if the URL has campaign parameter
					$out->showPermissionsErrorPage(
						[ [ 'badaccess-groups' ] ],
						'edit'
					);
					return;
				}

$1 needs to the list of groups, $2 needs to be the number of groups

Change 390980 had a related patch set uploaded (by Santhosh; owner: Santhosh):
[mediawiki/extensions/ContentTranslation@master] For invalid or missing campaign show error about enable beta feature

https://gerrit.wikimedia.org/r/390980

contributionsmenu entry point should only be accessible when CX is enabled, hence it is not listed in the campaigns.

Change 390980 merged by jenkins-bot:
[mediawiki/extensions/ContentTranslation@master] For invalid or missing campaign show error about enable beta feature

https://gerrit.wikimedia.org/r/390980

Checked in testwiki (wmf.8) - the user warning about ContentTranslation is displayed: