[Bug 1798872] Re: _pythonSymlinkCheck fails to account for use of update-alternatives

[michael]

On Wed, Oct 31, 2018, 7:41 AM Julian Andres Klode <
1798872 at bugs.launchpad.net wrote:

> So, you want to execute python in a subprocess and read its output?
>
> cosmic is also broken as documented in bug 1800823, as python is a
> symlink to python2.
>
> We probably should sanity check all of python, python2, python3.
>
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> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1798872
>
> Title:
>   _pythonSymlinkCheck fails to account for use of update-alternatives
>
> Status in ubuntu-release-upgrader package in Ubuntu:
>   New
>
> Bug description:
>   In order to deal with the fact that users often modify /usr/bin/python
> DistUpdgradeControler.py attempts to verify it is set to the correct
> version:
>   ...
>    fs_default_version = os.readlink('/usr/bin/python')
>    except OSError as e:
>                   logging.error("os.readlink failed (%s)" % e)
>                   return False
>               if not fs_default_version in (expected_default,
> os.path.join('/usr/bin', expected_default)):
>   ...
>
>   This check fails to account for setups using update-alternatives. In
>   this case /usr/bin/python always points to another symlink ( i.e
>   /etc/alternatives/python). This makes the above check always fail
>   regardless of the python version actually running.
>
>   sys.version_info should be used instead as it makes no assumptions
>   about how python was invoked.
>
>   "%s.%s.%s"
>   %(sys.version_info[0],sys.version_info[1],sys.version_info[2])"%s.%s.%s"
>   %(sys.version[0],sys.version_info[1],sys.version_info[2])
>
>   Yields the version string (i.e '2.7.15') for the running python
>   interpreter.
>
That would be one way. I was perposing the use of sys.version_info. This is
built-in python variable that tells what the currently running interpreter
version is regardless of how it was started. My understanding is that this
is intended as a compatibility check. In that case its the running python
version the should concern us.

>
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https://bugs.launchpad.net/bugs/1798872

Title:
  _pythonSymlinkCheck fails to account for use of update-alternatives

Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  In order to deal with the fact that users often modify /usr/bin/python DistUpdgradeControler.py attempts to verify it is set to the correct version:
  ...
   fs_default_version = os.readlink('/usr/bin/python')
   except OSError as e:
                  logging.error("os.readlink failed (%s)" % e)
                  return False
              if not fs_default_version in (expected_default, os.path.join('/usr/bin', expected_default)):
  ...

  This check fails to account for setups using update-alternatives. In
  this case /usr/bin/python always points to another symlink ( i.e
  /etc/alternatives/python). This makes the above check always fail
  regardless of the python version actually running.

  sys.version_info should be used instead as it makes no assumptions
  about how python was invoked.

  "%s.%s.%s"
  %(sys.version_info[0],sys.version_info[1],sys.version_info[2])"%s.%s.%s"
  %(sys.version[0],sys.version_info[1],sys.version_info[2])

  Yields the version string (i.e '2.7.15') for the running python
  interpreter.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1798872/+subscriptions