Summary and Info:

If I haven't updated in a while and try to install a package, the version of the package that I have in my local repo database cache may be removed from many of the mirrors. When pacman tries to install this package, it will look through the mirrors for a mirror that doesn't return 404. While this is happening there is no output from pacman.

This is a regression, previously it would print an error message right after every mirror it tried, but now all the error messages shows up at the end, either when it finds the package or when it has tried all the mirrors. I'm not sure exactly when the problem started, but I think it was some time this fall.

Here is an example. I ran `pacman -S mpc` and got this output:

```
resolving dependencies...
looking for conflicting packages...

Packages (1) mpc-0.33-3

Total Download Size: 0.04 MiB
Total Installed Size: 0.11 MiB

:: Proceed with installation? [Y/n]
:: Retrieving packages...
mpc-0.33-3-x86_64
```

It was like that for a while with no new output, and then after a while it printed the progress bar to the right of mpc, the error messages and the rest of the install output:

```
mpc-0.33-3-x86_64 45.8 KiB 509 KiB/s 00:00 [##########################################################################################################] 100%
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirror.archlinux.no : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirror.neuf.no : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirror.telepoint.bg : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirror.chaoticum.net : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirror.f4st.host : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from archmirror.it : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirror.lty.me : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from america.mirror.pkgbuild.com : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from ftp.sh.cvut.cz : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirror.pkgbuild.com : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from asia.mirror.pkgbuild.com : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from archlinux.mailtunnel.eu : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from archlinux.thaller.ws : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from arch.mirror.square-r00t.net : Failed to connect to arch.mirror.square-r00t.net port 443 after 5201 ms: Connection timed out
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirrors.neusoft.edu.cn : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from mirror.pseudoform.org : The requested URL returned error: 404
error: failed retrieving file 'mpc-0.33-3-x86_64.pkg.tar.zst' from europe.mirror.pkgbuild.com : The requested URL returned error: 404
(1/1) checking keys in keyring [##########################################################################################################] 100%
(1/1) checking package integrity [##########################################################################################################] 100%
(1/1) loading package files [##########################################################################################################] 100%
(1/1) checking for file conflicts [##########################################################################################################] 100%
(1/1) checking available disk space [##########################################################################################################] 100%
:: Processing package changes...
(1/1) installing mpc [##########################################################################################################] 100%
:: Running post-transaction hooks...
(1/1) Arming ConditionNeedsUpdate...
```

Note that the `mpc-0.33-3-x86_64` line was not printed twice, but the progress bar on the right only appeared after it found the package.

Instead of all of the errors showing up simultaneously at the end, each error should be printed when it occurs.


Steps to Reproduce:

1. Find a package that has been removed from many of your mirrors. Typically this happens if you haven't updated your machine for a while and try to install a package that has been updated in the repos.
2. Install that package.