[PD] error while loading shared libraries: libtk8.5.so.0

[Matteo Sisti Sette]

Hi,

A friend of mine has a dual-boot Mac with Mac OS and Ubuntu and uses 
Ubuntu very sporadically.

On Ubuntu, she has Pd-Extended installed which was installed more than a 
year ago and worked just fine the last-but-one time she booted Ubuntu.

Now after more than a year since last time, she booted Ubuntu, she 
didn't touch anything, and now Pd-Extended refuses to run, it says:

/usr/lib/pd-extended/bin/pd-gui: error while loading shared libraries: 
libtk8.5.so.0: cannot open shared object file: No such file or directory


The only way anything can be uninstalled or changed is through automatic 
updates.

Does anybody know how the needed library can have just disappeared and 
how to fix it? A package named "libtk" doesn't even seem to exist...

thanks
m.