Retracing the crash of window-buttons applet produced this error.
```
Traceback (most recent call last):
File "/usr/bin/apport-retrace", line 301, in <module>
options.dynamic_origins)
File "/usr/lib/python2.7/dist-packages/apport/sandboxutils.py", line 204, in make_sandbox
apport.fatal(str(e))
File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 35, in fatal
error(msg, *args)
File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 44, in error
sys.stderr.write(msg % args)
TypeError: not enough arguments for format string
```
ProblemType: Crash
DistroRelease: Ubuntu 16.04
Package: apport-retrace 2.20-0ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-15.31-generic 4.4.6
Uname: Linux 4.4.0-15-generic x86_64
ApportVersion: 2.20-0ubuntu3
Architecture: amd64
CrashCounter: 1
CurrentDesktop: GNOME-Flashback:Unity
Date: Sun Mar 27 17:32:09 2016
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/apport-retrace
InstallationDate: Installed on 2015-09-28 (180 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
InterpreterPath: /usr/bin/python2.7
PackageArchitecture: all
ProcCmdline: /usr/bin/python /usr/bin/apport-retrace -S system -C /home/username/.cache/apport/retrace -v --gdb /var/crash/_usr_lib_gnome-window-applets_windowbuttons.1000.crash
PythonArgs: ['/usr/bin/apport-retrace', '-S', 'system', '-C', '/home/username/.cache/apport/retrace', '-v', '--gdb', '/var/crash/_usr_lib_gnome-window-applets_windowbuttons.1000.crash']
SourcePackage: apport
Title: apport-retrace crashed with TypeError in error(): not enough arguments for format string
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip docker kismet libvirtd lp lpadmin lxd mail mythtv plugdev sambashare sudo vboxusers
Thank you for taking the time to report this bug and helping to make Ubuntu better. This kind of bug can still appear since apport still has code like "fatal(