I'm a bit befuddled by this: Since DisplayCAL 3.1.5, the 'lastmod_time' variable is populated from the value recorded statically in the file DisplayCAL/__version__.py that is part of the source archive, so the build is (and was) reproducible already [1], and the patch was unneeded. I see that the current build of DisplayCAL 3.1.6 is not reproducible in Debian testing, and the reason for this appears to be that the build does not use the pristine sources (probably the unneeded patch is being applied?).
So TLDR: Use the unmodified sources and all will be well. [1] http://download.opensuse.org/repositories/home:/fhoech/Debian_8.0/amd64/ http://download.opensuse.org/repositories/home:/fhoech:/testing/Debian_8.0/amd64/
