qapi: nail down convention that Errors sections are lists

By unstated convention, Errors sections are rST lists.  Document the
convention, and make the one exception conform.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240626222128.406106-10-jsnow@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/devel/qapi-code-gen.rst

@@ -1011,6 +1011,13 @@ like this::
 "Returns" and "Errors" sections are only valid for commands.  They
 document the success and the error response, respectively.
 
+"Errors" sections should be formatted as an rST list, each entry
+detailing a relevant error condition. For example::
+
+ # Errors:
+ #     - If @device does not exist, DeviceNotFound
+ #     - Any other error returns a GenericError.
+
 A "Since: x.y.z" tagged section lists the release that introduced the
 definition.
 

qapi/transaction.json

@@ -235,7 +235,7 @@
 #     additional detail.
 #
 # Errors:
-#     Any errors from commands in the transaction
+#     - Any errors from commands in the transaction
 #
 # Note: The transaction aborts on the first failure.  Therefore, there
 #     will be information on only one failed operation returned in an