Reported by Alex "FO-nTTaX" Winkler on wikitech-l:
The extension registration feature to depend on a specific skin by specification requires an extension to use the following example schema:

"requires": {
  "skins": {
    "Example": "*"
  }
}

However, the implementation actually looks for:

"requires": {
  "skin": {
    "Example": "*"
  }
}

See the misspelled key "skins" in the second example. This results in an exception if an extension implements the json according to the schema or to a schema violation, if an extension implements the json according to the implementation. The schema should win here, so let's fix the misspelled key (also, the extensions part uses the plural "extensions", too, instead of the singular "extension").