Do you see this message on some production wiki? This shouldn't happen normally, I think, and would indicate that someone tried to configure foreign uploads but did it wrong. If I just disable uploads locally, I see a simple "File uploads are disabled.":

Context helps.

$wgForeignUploadTargets on Wikitech is set to [ 'shared' ] (that's the default in [operations/mediawiki-config]/InitialiseSettings.php). The 'shared' repository corresponds to Wikimedia Commons on most production wikis ([operations/mediawiki-config]/filebackend.php). However, Wikitech doesn't use that, and instead sets $wgUseInstantCommons ($wmgUseClusterFileBackend), which uses a repository named 'wikimediacommons'. So the repository configured as upload target is missing, and you get this error message.

So there are two ways to fix this:

• Set $wgForeignUploadTargets to [ 'wikimediacommons' ] if we want uploads from inside the editor on Wikitech to go to Commons. Wikitech should already be able to use Commons' API, so this should just work.
• Set $wgForeignUploadTargets to [ 'local' ] if we want the files to be uploaded locally. Wikitech has uploads enabled. This might be the better option, since we want Wikitech to be mostly independent from the cluster.

Change 347422 had a related patch set uploaded (by Jforrester):
[operations/mediawiki-config@master] Wikitech: Don't try to do cross-wiki uploads to Commons

https://gerrit.wikimedia.org/r/347422

Change 347422 merged by jenkins-bot:
[operations/mediawiki-config@master] Wikitech: Don't try to do cross-wiki uploads to Commons

https://gerrit.wikimedia.org/r/347422

Mentioned in SAL (#wikimedia-operations) [2017-04-12T23:20:32Z] <catrope@tin> Synchronized wmf-config/InitialiseSettings.php: Disable cross-wiki uploads to Commons (T162374) (duration: 00m 43s)