[Bug 1754311] Re: package python-twisted-core 16.0.0-1 failed to install/upgrade: subprocess new pre-removal script returned error exit status 1

[DLPaktor]

Although, I must say that forces me to freeze my default  python

I would like to be able to "float" my default to the latest rev
(currently 3.6.4) without having to explicitly state a version when I
invoke it. Granted, not a terrible inconvenience, but a minor annoyance
nevertheless.

Any chance of tweaking the relevant processes (e.g.,  Software Updater
and the links in the  apt-get ...  chain) to explicitly invoke the
critical rev? I.e., where they call  python  and depend on the default
being frozen to  python2  (or  python2.7  which is where the sym-link
for  python2  was pointing), have them call  python2  (or  python2.7 )
explicitly, and allow the default to "float".

I think that would more correctly encapsulate the version dependencies.

Thanks.

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Title:
  package python-twisted-core 16.0.0-1 failed to install/upgrade:
  subprocess new pre-removal script returned error exit status 1

Status in twisted package in Ubuntu:
  New

Bug description:
  I installed python 3.6.4.

  Now when I run Software Updater, or  apt-get -f install  from the command-line,
  they crash.

  Software Updater puts up a message that:

  The package system is broken
  Check if you are using third party repositories. If so disable them, since they are a common source of problems.
  Furthermore run the following command in a Terminal: apt-get install -f

  
  Running  apt-get install -f  produced a cascade with the following highlight:

  Preparing to unpack .../python-twisted-core_16.0.0-1ubuntu0.2_all.deb ...
    File "/usr/bin/pyclean", line 63
      except (IOError, OSError), e:
                               ^
  SyntaxError: invalid syntax


  So I changed   File "/usr/bin/pyclean", line 63 to
      except (IOError, OSError) as e:

  
  The run of  apt-get install -f  now got:

  Preparing to unpack .../python-twisted-core_16.0.0-1ubuntu0.2_all.deb ...
  Traceback (most recent call last):
    File "/usr/bin/pyclean", line 32, in <module>
      from debpython.namespace import add_namespace_files
    File "/usr/share/python/debpython/namespace.py", line 120
      except (IOError, OSError), e:
                               ^

  
  I checked and, yes, File "/usr/share/python/debpython/namespace.py", line 120 has the same phrase.

  
  Breaking the update system prevents security updates from going through, so I am going to check the "security vulnerability" box as well.

  ProblemType: Package
  DistroRelease: Ubuntu 16.04
  Package: python-twisted-core 16.0.0-1
  ProcVersionSignature: Ubuntu 4.4.0-112.135-generic 4.4.98
  Uname: Linux 4.4.0-112-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.15
  Architecture: amd64
  Date: Thu Mar  8 01:37:43 2018
  ErrorMessage: subprocess new pre-removal script returned error exit status 1
  PackageArchitecture: all
  RelatedPackageVersions:
   dpkg 1.18.4ubuntu1.1
   apt  1.2.15ubuntu0.2
  SourcePackage: twisted
  Title: package python-twisted-core 16.0.0-1 failed to install/upgrade: subprocess new pre-removal script returned error exit status 1
  UpgradeStatus: No upgrade log present (probably fresh install)

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