Try to download existing images to save build time

publish_images.py

@@ -14,6 +14,16 @@ def main():
     for idx, fname in enumerate(dockerfiles):
         progress = "({}/{})".format(idx + 1, n_files)
 
+        print('-' * 79)
+        print("{} Checking for existing '{}'".format(progress, fname))
+        pull_cmd = ("docker pull {0}/{1}".format(REGISTRY_URL, fname))
+        child = sp.Popen(
+            pull_cmd, shell=True, stdout=sys.stdout, stderr=sp.PIPE)
+        child.communicate()
+        if child.returncode > 0:
+            print("  -> no image found for '{}', starting from scratch.".
+                  format(fname))
+
         print('-' * 79)
         print("{} Building '{}'".format(progress, fname))
         build_cmd = ("docker build --pull -t {0}/{1} -f {1} . ".format(
@@ -28,5 +38,6 @@ def main():
             push_cmd, shell=True, stdout=sys.stdout, stderr=sys.stderr)
         child.communicate()
 
+
 if __name__ == '__main__':
     main()