Cannot create single character tags when using a tag tree model

[mcrot]

I'm using tagulous version 0.14.1 and the following tag model (inside an app called "manager"):

import tagulous.models as tm
class TagModel(tm.TagTreeModel):
    class TagMeta:
        force_lowercase = True

During testing my app I see the following behaviour (on sqlite database):

I can create the tags projects/ABC and projects/AB without problems. The resulting tags
in the database are: ['projects', 'projects/AB', 'projects/ABC'].

Then, if I try to create the tag projects/A (only a single character label A), the library
tries to generate projects which is already there:

IntegrityError: duplicate key value violates unique constraint "manager_tagmodel_name_key"
DETAIL:  Key (name)=(projects) already exists.

Or, when starting fresh without any tags, the statement

TagModel.objects.create(name='projects/A') 

only creates the tag projects(without A). Is this expected behaviour?
I would expect that projects/A is a tag like projects/ABC.

[radiac]

Finally merged - thanks for the excellent patch, and once again sorry for the delay! This will be in the next release.