AAP-9450 Present useful message when engine is dead

[bhavenst]

Description

This PR adds a message "Deployment Engine unavailable, please re-deploy" when the login form receives a 502, which happens when the backend is timed out. This is a partial fix, since it doesn't take care of an already logged in screen. Maybe we should add a message on the UI that shows itself when the backend goes away too.

Commit message reminder

Commit messages are important because they will be used to build list of items included in Errata when the deployment driver container image is built and QE will use that list to figure out what to test before the image is published.

• For user facing features or fixes make sure Jira item number AAP-nnnnn is included in the commit message(s)
• For other changes, like unit tests or code refactoring, do not include Jira item numbers

PR task checklist

• [x] I have used appropriate commit messages based on section above
• [x] I have performed a self-review of my code
• [x] I have followed code style guidelines of this project
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] I have added thorough tests
• [x] I have had a successful deployment with the changes in this PR

Jira

This PR is for JIRA item: https://issues.redhat.com/browse/AAP-9450

Testing

Steps to test

1. Pull down the PR
2. Start deployment
3. Wait for engine to end naturally or connect to container and kill it ('server' process).
4. Attempt to log in, see new message.

Expected result

With the changes in this PR you will see a new message when attempting to log in when engine is down.

[bhavenst]

New commit changes Driver to Engine.

[bhavenst]

While this approach works and adds better handling of 502 error, we should follow up with a solution that checks status of the engine and present user with better, static page.

@tznamena Does this mean we need changes or OK as is?

Do you think we should also pop up a message on the main page if the backend goes away (GET on /steps starts failing, which could be a trigger).

[tznamena]

While this approach works and adds better handling of 502 error, we should follow up with a solution that checks status of the engine and present user with better, static page.

@tznamena Does this mean we need changes or OK as is?

Do you think we should also pop up a message on the main page if the backend goes away (GET on /steps starts failing, which could be a trigger).

This PR is OK as is, we will need another Jira work item to implement a status API for the engine and whole new static page. We can then add a logic that re-routes user to it once engine goes away.