I have a problem with a Tcl/Tk application, redet, and Ubuntu 18.04. I installed it in 17.04, using synaptic so that all its dependencies were pulled in. It continued to work in 17.10. After upgrading to 18.04 it failed to start with the following error messages.
Error in startup script: can't find package Itcl 3.4 while executing "package require Itcl 3.4" (file "/usr/share/tcltk/iwidgets4.1.0/iwidgets.tcl" line 18) invoked from within "source /usr/share/tcltk/iwidgets4.1.0/iwidgets.tcl" ("package ifneeded Iwidgets 4.1.0" script) invoked from within "package require Iwidgets" (file "/usr/bin/redet" line 27)
Although everything was unchanged, so I believe all dependencies were satisfied, I tried installing redet on a different machine with 18.04 installed using synaptic. All the same dependencies were pulled in, but when I tried to run redet I got the same error message. Googling, this problem appeared in the past on several message boards related to Tcl/Tk, but there is no obvious soution that I could understand. The only question I could find on AskUbuntu (Q: Problem to install fv tool) didn't have any responses.