Bump up required bazel version to 0.23

Change-Id: Iddff9a4c250f06a62f274e5c0389be9d567bcb60
diff --git a/Dockerfile b/Dockerfile
index 9f85dc6..0810ae9 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -17,7 +17,7 @@
 # build problems
 WORKDIR /src/onos
 RUN apt-get update && apt-get install -y zip python git bzip2 build-essential && \
-        curl -L -o bazel.sh https://github.com/bazelbuild/bazel/releases/download/0.19.0/bazel-0.19.0-installer-linux-x86_64.sh && \
+        curl -L -o bazel.sh https://github.com/bazelbuild/bazel/releases/download/0.23.0/bazel-0.23.0-installer-linux-x86_64.sh && \
         chmod +x bazel.sh && \
         ./bazel.sh --user && \
         export ONOS_ROOT=/src/onos && \
diff --git a/tools/build/bazel/bazel_version.bzl b/tools/build/bazel/bazel_version.bzl
index c6e88eb..49434bf 100644
--- a/tools/build/bazel/bazel_version.bzl
+++ b/tools/build/bazel/bazel_version.bzl
@@ -16,12 +16,12 @@
 
 def check_bazel_version():
     if "bazel_version" not in dir(native):
-        fail("\nBazel version is too old; please use 0.19.* official release!\n\n")
+        fail("\nBazel version is too old; please use 0.23.* official release!\n\n")
     elif not native.bazel_version:
-        print("\nBazel is not a release version; please use 0.19.* official release!\n\n")
+        print("\nBazel is not a release version; please use 0.23.* official release!\n\n")
         return
 
     versions = native.bazel_version.split(".")
-    if not int(versions[1]) >= 19:
-        fail("\nBazel version %s is not supported; please use 0.19.* official release!\n\n" %
+    if not int(versions[1]) >= 23:
+        fail("\nBazel version %s is not supported; please use 0.23.* official release!\n\n" %
              native.bazel_version)