[Debian-med-packaging] Bug#652320: altree FTBFS, /usr/bin/env: python: No such file or directory

[peter green]

package: altree
version: 1.0.1-5
severity: serious

altree failed to build on the armhf and s390x buildds with the following 
error

make[3]: Entering directory `/build/buildd-altree_1.0.1-5-armhf-eEc5cu/altree-1.0.1/Documentation'
         ======> building  fig/option_b.subfig.mk <======
/usr/bin/env: python: No such file or directory
make[3]: *** [fig/option_b.subfig.mk] Error 127

I was also able to reproduce this failure locally in pbuilder on amd64.

I do not know why the package built successfully on the other
autobuilders but I suspect that python was simply already installed
in the autobuilder chroots for some reason.

Please add python to the build-depends.