Using copied icons from other packages

[Joachim Zobel <jz-2017@heute-morgen.de>]

Hi.

I am currently packaging the tasmota device manager. This is mostly
straight forward. The upstream application does however contain an
icons.py file generated with pyrcc5. This contains non free icons that
I want to replace. Most of them can be replaced with icons already
existing in Debian. This will be done by using those to generate a
replacement icons.py. The others will be replaced with newly created
free licensed icons.

Is this acceptable with respect to policy? How do I handle copying the
Debian icons with respect to the copyright file? 

Sincerely,
Joachim

ITP: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1062335