Add support for default ca-cert files

Hi,

this branch addresses https://github.com/OfflineIMAP/offlineimap/issues/18.

I only tested it on Ubuntu, it works fine there.I collected the other location from a google
search, they may not be correct but there will be a info message (or should it be a warning instead?) if the distro is known but the location is wrong. There is also a message if its a linux distro that is not in the dict DISTRO_TO_CA_CERTFILE. So hopefully people start to contribute the correct location if I messed it up ;)

I added a test too, let me know if I did it right, the code seems to use a custom testrunner that I don't know. Also I would normally use python-mock but it
appears its not used yet in the code so instead of adding it I just added the trivial "MockUI" 
object.

Happy to fix any issues or do it differently, just say so! 

Thanks,
 Michael
On 15 September 2014 06:57, Michael Vogt <notifications@github.com> wrote:

> In offlineimap/utils.py:
>
> > +#    the Free Software Foundation; either version 2 of the License, or
> > +#    (at your option) any later version.
> > +#
> > +#    This program is distributed in the hope that it will be useful,
> > +#    but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +#    GNU General Public License for more details.
> > +#
> > +#    You should have received a copy of the GNU General Public License
> > +#    along with this program; if not, write to the Free Software
> > +#    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
> > +
> > +import platform
> > +import os
> > +
> > +DISTRO_CODENAME = platform.linux_distribution()[0]
>
> Hey muggenhor - thanks for your commend, thats a good point! I'm happy to
> change this, however given that this pull request is open since ~2years I
> don't want to spend time on it unless there is a reasonable chance that it
> might get merged by offlinemap upstream.
>
>
>
Well I think I'll just merge it.

RE:FreeBSD etc - packagers are free to patch other paths, or override the
correct location in the ~/.offlineimaprc file. However, I think it's good
to strive for automatically finding certificates on popular platforms.


-- 
Regards,

Dimitri.