I am having the same problem:


root@majestix:~# aptitude safe-upgrade 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Reading extended state information      
Initializing package states... Done
Writing extended state information... Done
Building tag database... Done             
The following packages will be upgraded:
  python-apt update-manager update-manager-core 
3 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0B/1122kB of archives. After unpacking 12.3kB will be used.
Do you want to continue? [Y/n/?] 
Writing extended state information... Done
(Reading database ... 113404 files and directories currently installed.)
Preparing to replace python-apt 0.7.4ubuntu4 (using .../python-apt_0.7.4ubuntu5_i386.deb) ...
Traceback (most recent call last):
  File "/usr/bin/pycentral", line 1593, in <module>
    main()
  File "/usr/bin/pycentral", line 1587, in main
    rv = action.run(global_options)
  File "/usr/bin/pycentral", line 1075, in run
    requested = pyversions.requested_versions_for_runtime(version_field, version_only=True)
  File "/usr/share/pycentral-data/pyversions.py", line 172, in requested_versions_for_runtime
    vinfo = parse_versions(vstring)
  File "/usr/share/pycentral-data/pyversions.py", line 58, in parse_versions
    raise ValueError, 'error parsing Python-Version attribute'
ValueError: error parsing Python-Version attribute
dpkg: error processing /var/cache/apt/archives/python-apt_0.7.4ubuntu5_i386.deb (--unpack):
 subprocess pre-installation script returned error exit status 1
Preparing to replace update-manager 1:0.87.6 (using .../update-manager_1%3a0.87.8_all.deb) ...
Traceback (most recent call last):
  File "/usr/bin/pycentral", line 1593, in <module>
    main()
  File "/usr/bin/pycentral", line 1587, in main
    rv = action.run(global_options)
  File "/usr/bin/pycentral", line 1075, in run
    requested = pyversions.requested_versions_for_runtime(version_field, version_only=True)
  File "/usr/share/pycentral-data/pyversions.py", line 172, in requested_versions_for_runtime
    vinfo = parse_versions(vstring)
  File "/usr/share/pycentral-data/pyversions.py", line 58, in parse_versions
    raise ValueError, 'error parsing Python-Version attribute'
ValueError: error parsing Python-Version attribute
dpkg: error processing /var/cache/apt/archives/update-manager_1%3a0.87.8_all.deb (--unpack):
 subprocess pre-installation script returned error exit status 1
Preparing to replace update-manager-core 1:0.87.6 (using .../update-manager-core_1%3a0.87.8_i386.deb) ...
Traceback (most recent call last):
  File "/usr/bin/pycentral", line 1593, in <module>
    main()
  File "/usr/bin/pycentral", line 1587, in main
    rv = action.run(global_options)
  File "/usr/bin/pycentral", line 1075, in run
    requested = pyversions.requested_versions_for_runtime(version_field, version_only=True)
  File "/usr/share/pycentral-data/pyversions.py", line 172, in requested_versions_for_runtime
    vinfo = parse_versions(vstring)
  File "/usr/share/pycentral-data/pyversions.py", line 58, in parse_versions
    raise ValueError, 'error parsing Python-Version attribute'
ValueError: error parsing Python-Version attribute
dpkg: error processing /var/cache/apt/archives/update-manager-core_1%3a0.87.8_i386.deb (--unpack):
 subprocess pre-installation script returned error exit status 1
Errors were encountered while processing:
 /var/cache/apt/archives/python-apt_0.7.4ubuntu5_i386.deb
 /var/cache/apt/archives/update-manager_1%3a0.87.8_all.deb
 /var/cache/apt/archives/update-manager-core_1%3a0.87.8_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install.  Trying to recover:
Reading package lists... Done             
Building dependency tree       
Reading state information... Done
Reading extended state information      
Initializing package states... Done
Building tag database... Done