Meaningful message when template suite isn't specify

[galitf]

lago init LagoInitFile
@ Initialize and populate prefix:

Initialize prefix:

* Create prefix dirs: 
* Create prefix dirs: Success (in 0:00:00)
* Generate prefix uuid: 
* Generate prefix uuid: Success (in 0:00:00)
* Create ssh keys: 
* Create ssh keys: Success (in 0:00:00)
* Tag prefix as initialized: 
* Tag prefix as initialized: Success (in 0:00:00)

Initialize prefix: Success (in 0:00:00)

Create disks for VM vm01:

* Create disk root: 
* Create disk root: ERROR (in 0:00:00)

Create disks for VM vm01: ERROR (in 0:00:00)

Missing current link, setting it to default

@ Initialize and populate prefix: ERROR (in 0:00:00)
Error occured, aborting
Traceback (most recent call last):
File "/usr/lib/python2.7/site-packages/lago/cmd.py", line 969, in main
cli_plugins[args.verb].do_run(args)
File "/usr/lib/python2.7/site-packages/lago/plugins/cli.py", line 184, in do_run
self._do_run(**vars(args))
File "/usr/lib/python2.7/site-packages/lago/cmd.py", line 194, in do_init
do_build=not skip_build,
File "/usr/lib/python2.7/site-packages/lago/prefix.py", line 1111, in virt_conf_from_stream
do_build=do_build
File "/usr/lib/python2.7/site-packages/lago/prefix.py", line 1226, in virt_conf
template_store=template_store,
File "/usr/lib/python2.7/site-packages/lago/prefix.py", line 1131, in _prepare_domains_images
template_store=template_store,
File "/usr/lib/python2.7/site-packages/lago/prefix.py", line 1153, in _prepare_domain_image
template_store=template_store,
File "/usr/lib/python2.7/site-packages/lago/prefix.py", line 1181, in _create_disks
template_store=template_store,
File "/usr/lib/python2.7/site-packages/lago/prefix.py", line 667, in _create_disk
template_store=template_store,
File "/usr/lib/python2.7/site-packages/lago/prefix.py", line 796, in _handle_template
template_repo=template_repo,
File "/usr/lib/python2.7/site-packages/lago/prefix.py", line 924, in _handle_lago_template
template = template_repo.get_by_name(template_spec['template_name'])
File "/usr/lib/python2.7/site-packages/lago/templates.py", line 388, in get_by_name
spec = self._dom.get('templates', {})[name]
KeyError: 'lago_functional_tests'

In LagoInitFile
We have the line:

• template_name: lago_functional_tests
  We should have in template repo file a template with this name

Need to run:
lago init LagoInitFile --template-repo-path template_repo.json