roachtest: install_flake failed

**Note:** This build has runtime assertions enabled. If the same failure was hit in a run without assertions enabled, there should be a similar failure without this message. If there isn't one, then this failure is likely due to an assertion violation or (assertion) timeout.

roachtest.install_flake [failed](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_RoachtestNightlyGceBazel/20622152?buildTab=log) with [artifacts](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_RoachtestNightlyGceBazel/20622152?buildTab=artifacts#/db-console/mixed-version-cypress) on master @ [cf01ffa5e9ecc35b63d7228cf113b74bcb809751](https://github.com/cockroachdb/cockroach/commits/cf01ffa5e9ecc35b63d7228cf113b74bcb809751):

```
| sudo chmod a+r /etc/apt/keyrings/docker.gpg;
|
| # Add the repository to Apt sources:
| echo \
| "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
| $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
| sudo tee /etc/apt/sources.list.d/docker.list > /dev/null;
| sudo apt-get update;
|
| # Install
| sudo apt-get install -y docker-ce;
| sudo usermod -aG docker ubuntu;
|
| # Verify
| sudo docker run hello-world
|
| ``````
| ... pt/sources.list.d/docker.list
| ++ dpkg --print-architecture
| ++ . /etc/os-release
| +++ PRETTY_NAME='Ubuntu 22.04.4 LTS'
| +++ NAME=Ubuntu
| +++ VERSION_ID=22.04
| +++ VERSION='22.04.4 LTS (Jammy Jellyfish)'
| +++ VERSION_CODENAME=jammy
| +++ ID=ubuntu
| +++ ID_LIKE=debian
| +++ HOME_URL=https://www.ubuntu.com/
| +++ SUPPORT_URL=https://help.ubuntu.com/
| +++ BUG_REPORT_URL=https://bugs.launchpad.net/ubuntu/
| +++ PRIVACY_POLICY_URL=https://www.ubuntu.com/legal/terms-and-policies/privacy-policy
| +++ UBUNTU_CODENAME=jammy
| ++ echo jammy
| + echo 'deb [arch=amd64 signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu jammy stable'
| + sudo apt-get update
| + sudo apt-get install -y docker-ce
| + sudo usermod -aG docker ubuntu
| + sudo docker run hello-world
| Unable to find image 'hello-world:latest' locally
| docker: Error response from daemon: Head "https://registry-1.docker.io/v2/library/hello-world/manifests/latest": received unexpected HTTP status: 503 Service Unavailable
|
| Run 'docker run --help' for more information
Wraps: (7) COMMAND_PROBLEM
Wraps: (8) exit status 125
Error types: (1) *withstack.withStack (2) *errutil.withPrefix (3) *withstack.withStack (4) *errutil.withPrefix (5) errors.TransientError (6) *hintdetail.withDetail (7) errors.Cmd (8) *exec.ExitError
Test: db-console/mixed-version-cypress
Messages: failed to install docker
(require.go:1357).NoError: FailNow called
(mixedversion.go:903).Run: panic (stack trace above): t.Fatal() was called
test artifacts and logs in: /artifacts/db-console/mixed-version-cypress/run_1
```

Parameters:
- arch=amd64
- cloud=gce
- coverageBuild=false
- cpu=4
- encrypted=false
- fs=ext4
- localSSD=true
- mvtDeploymentMode=shared-process
- mvtVersions=v24.1.12 → v24.3.0 → v25.1.4 → v25.2.6 → v25.4.0-alpha.2-dev-cf01ffa5e9ecc35b63d7228cf113b74bcb809751 (master)
- runtimeAssertionsBuild=true
- ssd=0
Help

See: [roachtest README](https://github.com/cockroachdb/cockroach/blob/master/pkg/cmd/roachtest/README.md)

See: [How To Investigate \(internal\)](https://cockroachlabs.atlassian.net/l/c/SSSBr8c7)

See: [Grafana](https://go.crdb.dev/roachtest-grafana/teamcity-20622152/db-console-mixed-version-cypress/1760950289202/1760950904743)

Same failure on other branches

- #155699 roachtest: install_flake failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-25.4]

/cc @cockroachdb/test-eng

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*install_flake.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Jira issue: CRDB-55579

Start with the roachtest README and the db-console/mixed-version-cypress failure log. Trace the Docker installation step that reaches registry-1.docker.io and returns HTTP 503, then inspect the related roachtest entry point and test artifacts. Done means the install_flake cause is identified and the test no longer fails for this transient installation error.

Written by the indexing model from the issue text.