diff --git a/core-builder/Dockerfile b/core-builder/Dockerfile
index 128f1739a4..812b2c4987 100644
--- a/core-builder/Dockerfile
+++ b/core-builder/Dockerfile
@@ -27,9 +27,10 @@ RUN \
 
 # dependencies for release script
 RUN \
+    # install env for python3
     apt-get update -y && \
-    apt-get install -y python-pip && \
-    pip install pyyaml && \
+    apt-get install -y python3-pip && \
+    pip3 install pyyaml && \
     apt-get remove -y --auto-remove && apt-get clean -y && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 WORKDIR /work
diff --git a/core-builder/Makefile b/core-builder/Makefile
index 678ee03bb3..2af9fad769 100644
--- a/core-builder/Makefile
+++ b/core-builder/Makefile
@@ -1,5 +1,5 @@
 DOCKER_IMAGE_NAME=seldonio/core-builder
-DOCKER_IMAGE_VERSION=0.2
+DOCKER_IMAGE_VERSION=0.3
 
 build_docker_image:
 	docker build --force-rm=true -t $(DOCKER_IMAGE_NAME):$(DOCKER_IMAGE_VERSION) .
diff --git a/release b/release
index c356c89fc1..9874e82f68 100755
--- a/release
+++ b/release
@@ -9,5 +9,5 @@ STARTUP_DIR="$( cd "$( dirname "$0" )" && pwd )"
 docker run --rm -it \
     -v ${HOME}/.m2:/root/.m2 \
     -v "${STARTUP_DIR}":/work \
-    seldonio/core-builder:0.2 python release.py "$@"
+    seldonio/core-builder:0.3 python3 release.py "$@"
 
diff --git a/release.py b/release.py
index 783fce6bad..5512b8e19c 100644
--- a/release.py
+++ b/release.py
@@ -3,7 +3,7 @@
 #
 
 import yaml
-import StringIO
+from io import StringIO
 import pprint
 from subprocess import Popen, PIPE
 import os
@@ -27,13 +27,13 @@ def dict_to_yaml(d):
     return yaml.dump(d, default_flow_style=False)
 
 def yaml_to_dict(yaml_data):
-    return yaml.load(StringIO.StringIO(yaml_data))
+    return yaml.load(StringIO(yaml_data))
 
 def run_command(args, debug=False):
     err, out = None, None
     if debug:
-        print "cwd[{}]".format(os.getcwd())
-        print "Executing: " + repr(args)
+        print("cwd[{}]".format(os.getcwd()))
+        print("Executing: " + repr(args))
     p = Popen(args, stdout=PIPE, stderr=PIPE)
     if p.wait() == 0:
         out = p.stdout.read()
@@ -51,7 +51,7 @@ def run_command(args, debug=False):
 def update_pom_file(fpath, seldon_core_version, debug=False):
     fpath = os.path.realpath(fpath)
     if debug:
-        print "processing [{}]".format(fpath)
+        print("processing [{}]".format(fpath))
     comp_dir_path = os.path.dirname(fpath)
     os.chdir(comp_dir_path)
     args = ["mvn", "versions:set", "-DnewVersion={seldon_core_version}".format(**locals())]
@@ -59,15 +59,15 @@ def update_pom_file(fpath, seldon_core_version, debug=False):
     ##pp(out)
     ##pp(err)
     if err == None:
-        print "updated {fpath}".format(**locals())
+        print("updated {fpath}".format(**locals()))
     else:
-        print "error {fpath}".format(**locals())
-        print err
+        print("error {fpath}".format(**locals()))
+        print(err)
 
 def update_chart_yaml_file(fpath, seldon_core_version, debug=False):
     fpath = os.path.realpath(fpath)
     if debug:
-        print "processing [{}]".format(fpath)
+        print("processing [{}]".format(fpath))
     f = open(fpath)
     yaml_data = f.read()
     f.close()
@@ -78,13 +78,13 @@ def update_chart_yaml_file(fpath, seldon_core_version, debug=False):
     with open(fpath, 'w') as f:
         f.write(dict_to_yaml(d))
 
-    print "updated {fpath}".format(**locals())
+    print("updated {fpath}".format(**locals()))
 
 
 def update_values_yaml_file(fpath, seldon_core_version, debug=False):
     fpath = os.path.realpath(fpath)
     if debug:
-        print "processing [{}]".format(fpath)
+        print("processing [{}]".format(fpath))
     f = open(fpath)
     yaml_data = f.read()
     f.close()
@@ -97,7 +97,7 @@ def update_values_yaml_file(fpath, seldon_core_version, debug=False):
     with open(fpath, 'w') as f:
         f.write(dict_to_yaml(d))
 
-    print "updated {fpath}".format(**locals())
+    print("updated {fpath}".format(**locals()))
 
 def update_core_jsonnet(fpath, seldon_core_version, debug=False):
     # eg.
@@ -113,7 +113,7 @@ def get_output_line(raw_line, srch_str):
 
     fpath = os.path.realpath(fpath)
     if debug:
-        print "processing [{}]".format(fpath)
+        print("processing [{}]".format(fpath))
 
     tmpfpath = fpath+'.tmp'
     with open(fpath, 'r') as f:
@@ -125,9 +125,9 @@ def get_output_line(raw_line, srch_str):
                         output_line = get_output_line(raw_line, srch_str)
                 ftmp.write(output_line)
         if debug:
-            print "created {tmpfpath}".format(**locals())
+            print("created {tmpfpath}".format(**locals()))
     shutil.move(tmpfpath, fpath) # move created tmp file to original file
-    print "updated {fpath}".format(**locals())
+    print("updated {fpath}".format(**locals()))
 
 def set_version(seldon_core_version, pom_files, chart_yaml_files, values_yaml_file, core_jsonnet_file, debug=False):
     # Normalize file paths
@@ -161,7 +161,7 @@ def main(argv):
     if opts.debug:
         pp(opts)
     set_version(opts.seldon_core_version, POM_FILES, CHART_YAML_FILES, VALUES_YAML_FILE, CORE_JSONNET_FILE, opts.debug)
-    print "done"
+    print("done")
 
 if __name__ == "__main__":
     main(sys.argv)