Improve directory handling

 - since dict_tools must be installed as a poetry dep on GHA, we can't
   rely on it being in a specific directory relative to the main repo;

 - so we need do a better job at setting the standard directories;

 - i've introduced DirUtils to handle that more or less globally.

lib/constants.py

@@ -1,5 +1,2 @@
-from os import path, environ
-import pathlib
-
 LT_VER = "6.4-SNAPSHOT"
 LATIN_1_ENCODING = 'ISO-8859-1'

tests/test_variant.py

@@ -1,9 +1,11 @@
 from lib.variant import Variant
+import lib.global_dirs as gd
 
 
 class TestVariant:
     """Test the Variant class."""
     def test_constructor(self):
+        gd.initialise_dir_utils('foo')
         variant = Variant('pt-BR')
         assert variant.lang == 'pt'
         assert variant.country == 'BR'