I can't use the scanner because Simple Scan (a.k.a. Document Scanner) does not
detect it.
## Steps to reproduce
1. guix install simple-scan
2. Connect the scanner.
3. Launch Simple Scan.
4. Click the Scan button in Simple Scan.
## Unexpected behavior
In step 3, Simple scan displays the following warning:
```
No scanners detected
Please check your scanner is connected and powered on
```
In step 4, you see the following message:
```
Failed to scan
No scanners available. Please connect a scanner.
```
## Expected behavior
* The scanner is detected in step 3 (no warning message is shown).
* Performing step 4 makes the scanner scan.
## System information
I'm using the Guix System and simple-scan 3.34.1:
```
$ LANG=C guix describe
Generation 5 Nov 04 2019 14:24:15 (current)
guix bf7b08c
repository URL: https://git.savannah.gnu.org/git/guix.git
branch: master
commit: bf7b08c4fe7d14c25a83bde99f19eca1119d88ff
```
## Additional information
The scanner works. I can use it from a Trisquel 8 Live USB stick, which comes
with Simple Scan.
Running simple-scan from a terminal displays the following warnings:
```
$ LANG=C simple-scan
(simple-scan:3953): Gtk-WARNING **: 18:42:44.193: Failed to register client:
GDBus.Error:org.gnome.SessionManager.AlreadyRegistered: Unable to register
client
```
---
https://sirgazil.bitbucket.io/
