[maemo-developers] Debmaster: Help for PyMaemo dependency hell on Fremantle?

[From: Jeremiah Foster]

On Sep 21, 2009, at 21:13, Thomas Wälti wrote:

> Hello Jeremiah

Hi Tom! (I'm CCing the development list as well, in case anyone else  
has this problem.)

> My name is Tom (maemo user twaelti) and I'm the developer of mClock.
> I've also used this application to create the pypackager and py2deb  
> wiki pages.
> Want I want to achieve is to make app development using Python  
> accessible for entry/casual developers.

Sounds great.

> [sbox-FREMANTLE_X86: ~/MyDocs/mclock] > apt-get install mclock
> Reading package lists... Done
> Building dependency tree... Done
> Some packages could not be installed. This may mean that you have
> requested an impossible situation or if you are using the unstable
> distribution that some required packages have not yet been created
> or been moved out of Incoming.
>
> Since you only requested a single operation it is extremely likely  
> that
> the package is simply not installable and a bug report against
> that package should be filed.
> The following information may help to resolve the situation:
>
> The following packages have unmet dependencies:
>   mclock: Depends: gnome-python (>= 2.26.1-1maemo1)
>           Depends: pygtk (>= 2.12.1-6maemo7) but it is not installable
>           Depends: pygame (>= 1.8.1release-0maemo3) but it is not  
> installable
> E: Broken packages
>
> Can you help me resolve this problem?

Here's your problem:
	Depends: pygtk (>= 2.12.1-6maemo7) but it is not installable
	Depends: pygame (>= 1.8.1release-0maemo3) but it is not installable

> More about the package can be found at http://maemo.org/packages/view/mclock/

Looking around a little more closely at the link you sent, I can see  
that you are also not identifying which section your software goes in.  
See this link for the warning: http://maemo.org/packages/package_instance/view/fremantle_extras-devel_free_i386/mclock/0.6.0

If you need more information on Maemo packaging policy (specifically  
where to place your software in the user/ tree) see this link: http://wiki.maemo.org/Task:Packaging_Policy_proposed_changes

> It depends on "python-gtk2 (>= 2.12.1-6maemo4), python-pygame (>=  
> 1.8.1release-0maemo1), gnome-python (>= 2.26.1-1maemo1), python- 
> hildon (>= 0.9.0-1maemo1), python-osso (>= 0.3-2maemo3)"
>
> My guess is that there is a problem with one of the underlying  
> dependenices, but how to find out?

The clearest message you receive is at the end of apt-get's run, when  
it says;
  	
	"The following packages have unmet dependencies:"

What has happened is that you depend on two python libraries that are  
newer than the libraries in the repos.

> Can you help me solve this issue?

The simplest way is for you to upload the required dependencies, or to  
use the existing dependencies with your software. This means there is  
extra work for you to do one way or the other - if you decide to  
upload newer versions of your dependencies, you'll have to package  
them yourself. If you go back and use the existing dependencies (which  
might be a good idea) then you will have to change your software to  
use different functions and / or libraries to get the functionality  
you need.

> I would like to have the app in the repo before the summit :-)

Three weeks left - but definitely doable.

> (I used apt-cache show... and also searched for the python packages  
> through http://maemo.org/packages/ , but don't know how to continue).

I think the best thing for you and your users (remember they are going  
to use the existing repos too) is for you to limit the amount of  
dependencies your software uses. Yes, this limits the functionality  
you can use and also limits the opportunity to use code already  
written, but it avoids hard to solve dependency problems. Of course,  
only you can decide exactly what balance you want to strike, but  
adapting your software to the existing libraries means you are more  
likely to have stable, well-tested dependencies.

Jeremiah
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