use variable to control if base image should be pulled

docker_build.py

@@ -174,4 +174,5 @@
         # TODO remove temp image
 
     docker_client = docker_api(base_url='unix://var/run/docker.sock')
+    pull = True
     builder = docker_client.build(
@@ -177,5 +178,5 @@
     builder = docker_client.build(
-        path='.', rm=True, pull=True, buildargs=buildargs,
+        path='.', rm=True, pull=pull, buildargs=buildargs,
         tag=image, dockerfile=dockerfile)
     # this is for python docker 1.8-1.9
     # TODO add compatibility with newer python docker