Debian package installation with dkpg works fine, but gdebi barfs on Debian 8 (Jessie).
So, before someone shows up complaining they can't install (because gdebi-gtk failed), here's the output and error message:
$ sudo gdebi ~/Downloads/Pencil-3.0.0-beta.1.deb
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done
Building data structures... Done
Traceback (most recent call last):
File "/usr/bin/gdebi", line 103, in <module>
debi.show_description()
File "/usr/share/gdebi/GDebi/GDsebiCli.py", line 96, in show_description
print(self._deb["Description"])
UnicodeEncodeError: 'ascii' codec can't encode character '\u2019' in position 40: ordinal not in range(128)
$ gdebi --version
0.9.5.5+nmu1