Description of problem:

Originally reported here
docker/compose#1577 (comment)

Using Dockerhub, doing a docker pull from a private repo works just fine. Running a docker build FROM that repo also works. But if you use docker build --pull, then the build fails with 'Error: image private_account/private_image:private_tag not found'

docker version:
Client version: 1.7.0
Client API version: 1.19
Go version (client): go1.4.2
Git commit (client): 0baf609
OS/Arch (client): darwin/amd64
Server version: 1.7.0
Server API version: 1.19
Go version (server): go1.4.2
Git commit (server): 0baf609
OS/Arch (server): linux/amd64

docker info:
Containers: 0
Images: 45
Storage Driver: aufs
Root Dir: /mnt/sda1/var/lib/docker/aufs
Backing Filesystem: extfs
Dirs: 45
Dirperm1 Supported: true
Execution Driver: native-0.2
Logging Driver: json-file
Kernel Version: 4.0.5-boot2docker
Operating System: Boot2Docker 1.7.0 (TCL 6.3); master : 7960f90 - Thu Jun 18 18:31:45 UTC 2015
CPUs: 4
Total Memory: 1.955 GiB
Name: boot2docker
ID: NO24:6XJP:RJXD:XRSQ:NQHC:FCFA:Z22R:AYRH:7QJR:QN4D:VBDI:TJFP
Debug mode (server): true
File Descriptors: 9
Goroutines: 17
System Time: 2015-06-20T00:12:49.612951271Z
EventsListeners: 0
Init SHA1:
Init Path: /usr/local/bin/docker
Docker Root Dir: /mnt/sda1/var/lib/docker
Username: rosskukulinski
Registry: https://index.docker.io/v1/

uname -a:
Darwin rossk-air.local 14.3.0 Darwin Kernel Version 14.3.0: Mon Mar 23 11:59:05 PDT 2015; root:xnu-2782.20.48~5/RELEASE_X86_64 x86_64

Environment details (AWS, VirtualBox, physical, etc.):

boot2docker

How reproducible:

Every time. Every, stinkin time.

Steps to Reproduce:

1. Create Dockerfile with FROM using private registry
2. docker build --pull .
3. See the error

Actual Results:

Error: image private_account/private_image:private_tag not found

Expected Results:

It should successfully pull the image and run the docker build.