Improve pull mirroring error message
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### Problem
The customer encountered the following error during the pull mirroring process.
```
{
"id": **,
"update_status": "failed",
"url": "https://*****:*****@gitlab.com/**/**/**.git",
"last_error": "9:Could not update main. Please refresh and try again..",
"last_update_at": "2025-01-29T13:53:06.360Z",
"last_update_started_at": "2025-01-29T13:53:05.218Z",
"last_successful_update_at": "2025-01-29T11:07:06.717Z",
"enabled": true,
"mirror_trigger_builds": true,
"only_mirror_protected_branches": true,
"mirror_overwrites_diverged_branches": true,
"mirror_branch_regex": null
}
```
The root cause was identified: the mirror user didn't have force push permissions on the branch to allow to overwrite divergence.
### Proposal
1. Try to reproduce this problem based on the report
2. Consider improving the error message to make it clearer.
issue