SIEM fails to load when ja-JP is the locale in v7.7.1

[mattkime]

Description:

Set i18n Japanese locale in Kibana prevents access to SIEM app.

Following error shows up when accessing the SIEM app:

Version: 7.7.1
Build: 30896
Error: [I18n] Error formatting message: "xpack.siem.case.connectors.servicenow.selectMessageText" for locale: "ja-jp".
SyntaxError: Expected "\\#", "\\\\", "\\u", "\\{", "\\}", "{", [^{}\\\0-\x1F\x7f \t\n\r], end of input or whitespace but "\\" found.
    at Object.t.translate (http://localhost:5601/bundles/kbn-ui-shared-deps/kbn-ui-shared-deps.js:312:87058)
    at Object.4444 (http://localhost:5601/bundles/siem.bundle.js:14:172286)
    at __webpack_require__ (http://localhost:5601/bundles/siem.bundle.js:2:1595)
    at Object.4440 (http://localhost:5601/bundles/siem.bundle.js:14:157708)
    at __webpack_require__ (http://localhost:5601/bundles/siem.bundle.js:2:1595)
    at Object.4439 (http://localhost:5601/bundles/siem.bundle.js:14:157323)
    at __webpack_require__ (http://localhost:5601/bundles/siem.bundle.js:2:1595)
    at Object.4406 (http://localhost:5601/bundles/siem.bundle.js:10:157933)
    at __webpack_require__ (http://localhost:5601/bundles/siem.bundle.js:2:1595)
    at Object.4405 (http://localhost:5601/bundles/siem.bundle.js:10:157069)

Steps to reproduce

1. Set i18n.locale: "ja-JP" in kibana.yml
2. Restart Kibana
3. Go to Kibana SIEM app

Screenshot

Workaround

Switch temporarily back to locale default ("en").

[elasticmachine]

Pinging @elastic/kibana-localization (Team:Localization)

[mattkime]

Does not seem to happen on v7.8

[Bamieh]

I am working on a PR this week to start checking for this case in the i18n_check script to avoid this happening again. I'll run the script on master, 7.7, 7.8 and 7.x once its ready and submit PRs if needed.

Related: #68220

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)