WORKSPACE: remove nixpkgs/rules_nix

We're not using them for anything. Initially they were going to be used
for nixops, but nixops is not very good, so let's just drop them.

We still have a Nix dependency for clustercfg.py when provisioning
nodes, but rules_nix/nixpkgs in WORKSPACE were unrelated to that.

Change-Id: I28c249507d1be9c5dbbd1ee764deccd9ab038549
diff --git a/WORKSPACE b/WORKSPACE
index 138b93a..268259b 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -105,29 +105,6 @@
 
 container_repositories()
 
-# Nix rules
-http_archive(
-    name = "io_tweag_rules_nixpkgs",
-    strip_prefix = "rules_nixpkgs-33c50ba64c11dddb95823d12f6b1324083cc5c43",
-    urls = ["https://github.com/tweag/rules_nixpkgs/archive/33c50ba64c11dddb95823d12f6b1324083cc5c43.tar.gz"],
-    sha256 = "91fedd5151bbd9ef89efc39e2172921bd7036c68cff54712a5df8ddf62bd6922",
-)
-
-# Nix packages
-
-load("@io_tweag_rules_nixpkgs//nixpkgs:nixpkgs.bzl", "nixpkgs_git_repository", "nixpkgs_package")
-
-nixpkgs_git_repository(
-    name = "nixpkgs",
-    revision = "2f1f9a9fe8a3c22f0677733523eaf6bd33995d50",
-)
-
-nixpkgs_package(
-    name = "nixops",
-    attribute_path = "nixops",
-    repositories = {"nixpkgs": "@nixpkgs"},
-)
-
 # Python rules
 
 git_repository(
diff --git a/cluster/tools/install.sh b/cluster/tools/install.sh
index 08e3476..6f32fbb 100755
--- a/cluster/tools/install.sh
+++ b/cluster/tools/install.sh
@@ -15,9 +15,3 @@
         //cluster/tools:calicoctl \
         //cluster/tools:cfssl
 
-if [ ! -e /nix ] ; then
-    echo "WARNING: No Nix installation detected. nix-dependent tools (nixops) will not be built or available." 
-else
-    bazel build \
-            //cluster/tools:nixops
-fi