Inconsistant stderr/stdout results and no reasons reported on match issue.

### Problem

If I run beet import -q on a folder I've already imported, it forwards the error output to **stderr**.

```
This album is already in the library!
Skipping.
```

if I run beet import -q on a new folder, but it still skips because of a match issue, it forwards the output to **stdout** without a reason:

```
/home/path/album (12 items)
Skipping.
```

I'm trying to setup some automation, and looking for some consistency for reporting on completion of import tasks that require manual intervention.

Start by reproducing the two `beet import -q` cases described in the issue and trace where their output is written. Compare the already-imported and match-issue skip paths, then make their stream behavior consistent and ensure the match-issue case reports a reason. Done means both outcomes are predictable for automation.

Written by the indexing model from the issue text.