Initial ROS 2 support.

The basic packages build, but there is no guarantee that they work correctly.

colcon/cmake.nix

@@ -0,0 +1,35 @@
+{ lib, buildPythonPackage, fetchPypi, isPy27, colcon-core, colcon-library-path
+, colcon-test-result, cmake }:
+
+buildPythonPackage rec {
+  pname = "colcon-cmake";
+  version = "0.2.13";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "1xslh52d91zs0vsa10himckjh2frq54awxq6n68k6jv7h6yiyb7m";
+  };
+
+  postPatch = ''
+    substituteInPlace colcon_cmake/task/cmake/__init__.py \
+      --replace "'cmake'" "'${cmake}/bin/cmake'"
+  '';
+
+  propagatedBuildInputs = [
+    colcon-core
+    colcon-library-path
+    colcon-test-result
+  ];
+
+  # Requires unpackaged dependencies
+  doCheck = false;
+
+  disabled = isPy27;
+
+  meta = with lib; {
+    description = "An extension for colcon-core to support CMake projects.";
+    homepage = "https://colcon.readthedocs.io";
+    license = licenses.asl20;
+    maintainers = with maintainers; [ lopsided98 ];
+  };
+}