docker pull <invalid image> errors out with traceback

[concaf]

Invalid image name still errors out with traceback after #441's resolution.

[vagrant@centos7-adb atomicapp]$ sudo atomicapp --verbose run foo --provider docker
2016-02-22 08:57:56,036 - [INFO] - main.py - Action/Mode Selected is: run
2016-02-22 08:57:56,036 - [DEBUG] - main.py - Final parsed cmdline: run --verbose foo --provider docker
2016-02-22 08:57:56,036 - [DEBUG] - main.py - NuleculeManager init app_path: /var/lib/atomicapp/foo-4714d136e9ec
2016-02-22 08:57:56,036 - [DEBUG] - main.py - NuleculeManager init image: foo
2016-02-22 08:57:56,037 - [DEBUG] - main.py - Request to unpack to foo to /var/lib/atomicapp/foo-4714d136e9ec
2016-02-22 08:57:56,037 - [INFO] - base.py - Unpacking image: foo to /var/lib/atomicapp/foo-4714d136e9ec
2016-02-22 08:57:56,159 - [INFO] - container.py - Pulling Docker image: foo
2016-02-22 08:57:56,159 - [DEBUG] - container.py - /usr/bin/docker pull foo
Using default tag: latest
Trying to pull repository docker.io/library/foo ... not found
Error: image library/foo:latest not found
2016-02-22 08:58:01,405 - [ERROR] - main.py - Could not pull Docker image foo
Traceback (most recent call last):
File "/home/vagrant/atomicapp/atomicapp/cli/main.py", line 101, in cli_run
nm.run(**argdict)
File "/home/vagrant/atomicapp/atomicapp/nulecule/main.py", line 224, in run
self.nulecule = self.unpack(dryrun=dryrun, config=self.answers)
File "/home/vagrant/atomicapp/atomicapp/nulecule/main.py", line 129, in unpack
nodeps=nodeps, dryrun=dryrun, update=update)
File "/home/vagrant/atomicapp/atomicapp/nulecule/base.py", line 104, in unpack
docker_handler.pull(image)
File "/home/vagrant/atomicapp/atomicapp/nulecule/container.py", line 63, in pull
raise Exception("Could not pull Docker image %s" % image)
Exception: Could not pull Docker image foo