Handle Oauth2 ImplementationUnavailableError in monzo

[wmoss]

Proposed change

As described in much more detail in PR #154579 and this blog post, previously, if there was no internet and the call to fetch cloud services fail, integrations like this one using cloud oauth2 would terminally fail. #154579 introduced config_entry_oauth2_flow.ImplementationUnavailableError and raises it in that specific case. This catches that error and raises ConfigEntryNotReady so that the configuration will be retried when internet is available again.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue: Fix account link no internet on startup #154579
• Link to documentation pull request:
• Link to developer documentation pull request:
• Link to frontend pull request:

Checklist

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[home-assistant]

Hey there @JakeMartin-ICL, mind taking a look at this pull request as it has been labeled with an integration (monzo) you are listed as a code owner for? Thanks!

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[Copilot]

Pull request overview

Updates the Monzo integration to gracefully handle the new OAuth2 “implementation unavailable” error (introduced in #154579) by retrying config entry setup when the underlying OAuth implementation cannot be fetched (e.g., no internet).

Changes:

• Catch ImplementationUnavailableError during Monzo config entry setup and raise ConfigEntryNotReady with a translated message.
• Add Monzo translation strings for the oauth2_implementation_unavailable exception message.
• Add a unit test asserting the config entry transitions to SETUP_RETRY when the OAuth implementation is unavailable.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
homeassistant/components/monzo/__init__.py	Converts OAuth implementation lookup failures into ConfigEntryNotReady so setup is retried instead of terminally failing.
homeassistant/components/monzo/strings.json	Adds the exception translation key wired to the common OAuth2 implementation unavailable message.
tests/components/monzo/test_init.py	Adds coverage to ensure setup enters retry state when ImplementationUnavailableError is raised.