samba-tool ImportError: No module named param

Alexander Bokovoy ab at
Wed Dec 12 17:08:43 UTC 2018

On ke, 12 joulu 2018, Noel Power via samba-technical wrote:
> On 12/12/2018 16:08, Volker Lendecke wrote:
> > On Wed, Dec 12, 2018 at 03:49:46PM +0000, Noel Power via samba-technical wrote:
> > > the default make builds and installs python3 products, the import statement
> > > if failing because you are running ./bin/samba-tool (which by default on
> > > your system is running with python2 because of the shebang)
> > > 
> > > if you run python3 ./bin/samba-tool  it will work
> > > 
> > > So, why haven't we changed the shebang to python3, there is currently some
> > > discussion ongoing about that. It's not as clear cut as you think. In
> > > general though scripts that are deliberately written to run with python2 &
> > > python3 can have python in the shebang line. You need to be aware what
> > > /usr/bin/python (or wherever it is located) is pointing at, in a system that
> > > has python2 and python3 it might be /usr/bin/python could be a link to
> > > either (and certainly in some newer enterprise focused distros I will bet
> > > soon python -> python3), additionally you need to be aware of what your
> > > build targets python2 or python3
> > The python community really was smoking weird stuff when designing a
> > completely new and incompatible language, naming it the same as the
> > one before.
> that's not quite true, the recommendation  is new code should use a shebang
> appropriate to the version that is targetted python2 or python3 (or even
> more finely grained python2.x or python3.x etc.) The exception is code that
> is designed to work with both. /usr/bin/python in modern systems is a
> placeholder (e.g. a link) the actual scripting interpreters are python2 &
> python3 so it kindof makes sense to have the shebang names as it is to
> reflect that.
It is more complex than that. PEP-0394 ( 
says, among other things:

- If the python command is installed, it should invoke the same version
  of Python as the python2 command

- One exception to this is scripts that are deliberately written to be
  source compatible with both Python 2.x and 3.x. Such scripts may
  continue to use python on their shebang line.

- When packaging software that is source compatible with both versions,
  distributions may change such python shebangs to python3. This ensures
  software is used with the latest version of Python available, and it
  can remove a dependency on Python 2.

On Fedora side I'm firmly in the camp with the latter statement. This
allows us a chance to eventually get rid of Python 2 at all. Fedora
ships python-unversioned-command package which introduces
/usr/bin/python as /usr/bin/python2 symlink. If you wouldn't install
this package, you have no /usr/bin/python at all.

> > We should make a blocker bug for 4.10. We can't ship with this mess.
> it isn't as much of a mess as you think, the problem is that we probably
> should be replacing the shebang on any python scripts (or tools) that are
> delivered as part of the build (depending on which python version is
> targetted). This is already something we are discussing but it is good to
> get feedback. That's the purpose of getting in early into master so we can
> iron these things out
Yep. But having a bug serves several purposes here:
 - it ensures the work is completed before the release
 - it ensures the change or a choice of change is documentated in
   release notes
 - it ensures distributions are picking the change up

/ Alexander Bokovoy

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