Assure that a project directory has a cache folder.
    If not, it will create it.

def assure_cache(project_path=None):
    """
    Assure that a project directory has a cache folder.
    If not, it will create it.
    """

    project_path = path(project_path, ISDIR)
    cache_path = os.path.join(project_path, CACHE_NAME)

    if not os.path.isdir(cache_path):
        os.mkdir(cache_path)