Herokuish update fails if existing herokuish is used by other containers,
using docker build --pull will force to update also the base image.
Setting up herokuish (0.3.28) ...
Removing old herokuish image
Failed to remove image (gliderlabs/herokuish): Error response from daemon: conflict: unable to remove repository reference "gliderlabs/herokuish" (must force) - container dbf2298ab5a5 is using its referenced image 7d4a8d661476
Importing herokuish into docker (around 5 minutes)
