We already throw around some exceptions that are localized
(ErrorPageError and its subclasses, MalformedTitleException), but
there's no standard way to recognize them. Let's change that.
Then let's use them in the API to be able to have internationalized
errors when such exceptions are caught, instead of wrapping the
English-language version.
Change-Id: Iac7c90f92a889f8de9dae373547c07b884addaea
API warnings and error messages are currently hard-coded English
strings. This patch changes that.
With a few exceptions, this patch should be compatible with non-updated
extensions:
* The change to ApiBase::$messageMap will blow up anything trying to
mess with it.
* The changes to the 'ApiCheckCanExecute' hook will cause a wrong
(probably unparsed) error message to be emitted for extensions not
already using an ApiMessage. Unless they're currently broken like
Wikibase.
Bug: T37074
Bug: T47843
Depends-On: Ia2b66b57cd4eaddc30b3ffdd7b97d6ca3e02d898
Depends-On: I2e1bb975bb0045476c03ebe6cdec00259bae22ec
Depends-On: I53987bf87c48f6c00deec17a8e957d24fcc3eaa6
Depends-On: Ibf93a459eb62d30f7c70d20e91ec9faeb80d10ed
Depends-On: I3cf889811f44a15935e454dd42f081164d4a098c
Depends-On: Ieae527de86735ddcba34724730e8730fb277b99b
Depends-On: I535344c29d51521147c2a26c341dae38cec3e931
Change-Id: Iae0e2ce3bd42dd4776a9779664086119ac188412
