python.pkgs.python-axolotl: move to a separate file

pkgs/development/python-modules/python-axolotl/default.nix

···
+{ lib, buildPythonPackage, fetchurl, python-axolotl-curve25519, protobuf, pycrypto }:
+
+buildPythonPackage rec {
+  name = "python-axolotl-${version}";
+  version = "0.1.39";
+
+  src = fetchurl {
+    url = "mirror://pypi/p/python-axolotl/${name}.tar.gz";
+    sha256 = "09bf5gfip9x2wr0ij43p39ac6z2iqzn7kgpi2jjbwpnhs0vwkycs";
+  };
+
+  propagatedBuildInputs = [ python-axolotl-curve25519 protobuf pycrypto ];
+  # IV == 0 in tests is not supported by pycryptodome (our pycrypto drop-in)
+  doCheck = false;
+
+  meta = with lib; {
+    homepage = https://github.com/tgalal/python-axolotl;
+    description = "Python port of libaxolotl-android";
+    maintainers = with maintainers; [ abbradar ];
+    license = licenses.gpl3;
+  };
+}

pkgs/top-level/python-packages.nix

···
     };
   };
 
-  python-axolotl = buildPythonPackage rec {
-    name = "python-axolotl-${version}";
-    version = "0.1.39";
-
-    src = pkgs.fetchurl {
-      url = "mirror://pypi/p/python-axolotl/${name}.tar.gz";
-      sha256 = "09bf5gfip9x2wr0ij43p39ac6z2iqzn7kgpi2jjbwpnhs0vwkycs";
-    };
-
-    propagatedBuildInputs = with self; [ python-axolotl-curve25519 protobuf pycrypto ];
-    # IV == 0 in tests is not supported by pycryptodome (our pycrypto drop-in)
-    doCheck = false;
-
-    meta = {
-      homepage = "https://github.com/tgalal/python-axolotl";
-      description = "Python port of libaxolotl-android";
-      maintainers = with maintainers; [ abbradar ];
-      license = licenses.gpl3;
-      platforms = platforms.all;
-    };
-  };
+  python-axolotl = callPackage ../development/python-modules/python-axolotl { };
 
   python-axolotl-curve25519 = buildPythonPackage rec {
     name = "python-axolotl-curve25519-${version}";