trap ERR debug stacktrace printing

[Evan Benn]

Hello,

I am attempting to fix a debug stack trace printer.

https://stackoverflow.com/questions/60483579/bash-err-trap-discards-value-of-args-of-the-failing-command

I have explained the issue there, but basically BASH_COMMAND contains
the failing command and args, but variables are unexpanded making the
trace not particularly useful.

The failing command is evicted from BASH_ARGV by the time trap ERR runs.

Thanks