Fix debian release build

release/debian/Dockerfile

@@ -15,7 +15,6 @@ ARG REF
 
 RUN git reset --hard $REF
 ADD debian debian
-RUN cp LICENSE debian/copyright
 ADD git2debchangelog.sh .
 RUN /bin/bash git2debchangelog.sh > debian/changelog
 

release/debian/debian/copyright

+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Upstream-Name: graph-tool
+Upstream-Contact: Tiago de Paula Peixoto <tiago@skewed.de>
+Source: https://graph-tool.skewed.de
+
+Files: *
+Copyright: 2006-2020 Tiago de Paula Peixoto
+License: LGPL-3+