package supervisor 3.0a8-1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Walter Scheper]

Release 11.04

supervisor:
  Installed: 3.0a8-1
  Candidate: 3.0a8-1
  Version table:
 *** 3.0a8-1 0
        500 http://mirror.cc.columbia.edu/pub/linux/ubuntu/archive/ natty/universe amd64 Packages
        100 /var/lib/dpkg/status

I expected the supervisor package to be installed and instead installation failed with a python ImportError: cannot import name fixtag

ProblemType: Package
DistroRelease: Ubuntu 11.04
Package: supervisor 3.0a8-1
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic x86_64
NonfreeKernelModules: fglrx
AptOrdering: supervisor: Configure
Architecture: amd64
Date: Tue Jul 19 14:06:30 2011
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110426)
PackageArchitecture: all
SourcePackage: supervisor
Title: package supervisor 3.0a8-1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)