I'm having some trouble to have the album plug-in working.

With ikiwiki version 3.20170111 installed via pkgsrc on macOS 10.12.4, I installed the album plugin for Ikiwiki following the instruction in the section 'Manual installation' at https://ikiwiki.info/plugins/contrib/album/.  The problem is that after 'ikiwiki --rebuild --verbose --setup mysite.setup --gettime', the page with

```
# Images
[[!sidebar content=""]]
[[!album 
  sort="age"
  size="full"
  thumbnailsize="96x96"
  viewertemplate="albumviewer"
  prevtemplate="albumprev"
  nexttemplate="albumnext"]]
```

builds correctly into an page with a list of images, but if I click any individual thumbnail to get to a page that's supposed to contain just that one image, I see the following exposed code 

```
[[!albumimage Error: template albumviewer not found]]
```

I verified that I do have albumviewer.tmpl in sourcedir/templates/.

Any idea why and how to fix it?
