duplicity: add setuptools_scm dependency

pkgs/tools/backup/duplicity/default.nix

@@ -1,5 +1,4 @@
 { lib, stdenv
-, fetchpatch
 , fetchurl
 , pythonPackages
 , librsync
@@ -9,7 +8,6 @@
 , par2cmdline
 , util-linux
 , rsync
-, backblaze-b2
 , makeWrapper
 , gettext
 }:
@@ -34,13 +32,17 @@ pythonPackages.buildPythonApplication rec {
     # to make the testing code stop assuming it is run from the source directory.
     ./use-installed-scripts-in-test.patch
   ] ++ lib.optionals stdenv.isLinux [
+    # Broken on Linux in Nix' build environment
     ./linux-disable-timezone-test.patch
   ];
 
+  SETUPTOOLS_SCM_PRETEND_VERSION = version;
+
   nativeBuildInputs = [
     makeWrapper
     gettext
     pythonPackages.wrapPython
+    pythonPackages.setuptools-scm
   ];
   buildInputs = [
     librsync