##### SUMMARY
As a nicety to the user, `ansible-galaxy collection` should check certain properties of the `collection_name` argument, and provide helpful suggestions about expected format.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
lib/ansible/galaxy/collection.py

##### ADDITIONAL INFORMATION
When getting this message, it's not clear to the user what they should do differently:

```yaml
$ ansible-galaxy collection install chrismeyersfsu_tower_modules -p alan -vvv
ansible-galaxy 2.9.0.dev0
  config file = None
  configured module search path = ['/Users/alancoding/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/alancoding/Documents/repos/ansible/lib/ansible
  executable location = /Users/alancoding/.virtualenvs/ansible3/bin/ansible-galaxy
  python version = 3.6.5 (default, Apr 25 2018, 14:23:58) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]
No config file found; using defaults
Opened /Users/alancoding/.ansible_galaxy
 [WARNING]: The specified collections path '/Users/alancoding/Documents/repos/jlaska-ansible-playbooks/alan' is not part of the configured Ansible collections paths
'/Users/alancoding/.ansible/collections:/usr/share/ansible/collections'. The installed collection won't be picked up in an Ansible run.

Found installed collection chrismeyersfsu.tower_modules:0.0.1 at '/Users/alancoding/Documents/repos/jlaska-ansible-playbooks/alan/ansible_collections/chrismeyersfsu/tower_modules'
Processing requirement collection 'chrismeyersfsu_tower_modules'
ERROR! Unexpected Exception, this is probably a bug: not enough values to unpack (expected 2, got 1)
the full traceback was:

Traceback (most recent call last):
  File "/Users/alancoding/Documents/repos/ansible/bin/ansible-galaxy", line 111, in <module>
    exit_code = cli.run()
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/cli/galaxy.py", line 269, in run
    context.CLIARGS['func']()
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/cli/galaxy.py", line 617, in execute_install
    no_deps, force, force_deps)
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/galaxy/collection.py", line 450, in install_collections
    force, force_deps, no_deps)
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/galaxy/collection.py", line 831, in _build_dependency_map
    validate_certs, (force or force_deps))
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/galaxy/collection.py", line 898, in _get_collection_info
    parent=parent)
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/galaxy/collection.py", line 296, in from_name
    namespace, name = collection.split('.', 1)
ValueError: not enough values to unpack (expected 2, got 1)
```

Instead of `ValueError`, it would be better to give text like

> Improperly formatted collection name argument. Collection name must be of the format "username.collection_name", like "chrismeyersfsu.tower_modules"

''' Creates a collection artifact tarball that is ready to be published and installed '''
    output_dir = to_text(tmp_path_factory.mktemp('test-ÅÑŚÌβŁÈ Output'))
    # Because we call GalaxyCLI in collection_skeleton we need to reset the singleton back to None so it uses the new
    # args, we reset the original args once it is done.
    orig_cli_args = co.GlobalCLIArgs._Singleton__instance
    try:
        co.GlobalCLIArgs._Singleton__instance = None
        galaxy_args = ['ansible-galaxy', 'collection', 'build', collection_skeleton, '--output-path', output_dir]
        gc = GalaxyCLI(args=galaxy_args)
        gc.run()
        yield output_dir
    finally:
        co.GlobalCLIArgs._Singleton__instance = orig_cli_args
def test_invalid_skeleton_path():
    expected = "- the skeleton path '/fake/path' does not exist, cannot init collection"
    gc = GalaxyCLI(args=['ansible-galaxy', 'collection', 'init', 'my.collection', '--collection-skeleton',
                         '/fake/path'])
    with pytest.raises(AnsibleError, match=expected):
        gc.run()
@pytest.mark.parametrize("name", [
    "",
    "invalid",
    "hypen-ns.collection",
    "ns.hyphen-collection",
    "ns.collection.weird",
])
def test_invalid_collection_name(name):