Fix data written by dictionary_pickler.py

The changes to the return types of `DictionaryFactory.get_dictionary()`
in 63933fc broke the generation of dictionaries using
`training/dictionary_pickler.py`. This commit fixes that again, by
undoing the changes to `training/dictionary_pickler.py` made by 63933fc.

training/dictionary_pickler.py

@@ -10,7 +10,7 @@
 import re
 from operator import itemgetter
 from pathlib import Path
-from typing import Dict, List, Optional
+from typing import ByteString, Dict, List, Optional
 
 import simplemma
 from simplemma.strategies.defaultrules import DEFAULT_RULES
@@ -49,7 +49,9 @@ def _determine_path(listpath: str, langcode: str) -> str:
     return str(Path(__file__).parent / filename)
 
 
-def _read_dict(filepath: str, langcode: str, silent: bool) -> Dict[str, str]:
+def _read_dict(
+    filepath: str, langcode: str, silent: bool
+) -> Dict[ByteString, ByteString]:
     mydict: Dict[str, str] = {}
     myadditions: List[str] = []
     i: int = 0
@@ -120,12 +122,12 @@ def _read_dict(filepath: str, langcode: str, silent: bool) -> Dict[str, str]:
         mydict[word] = word
     LOGGER.debug("%s %s", langcode, i)
     # sort and convert to bytestrings
-    return dict(sorted(mydict.items()))
+    return {k.encode("utf-8"): v.encode("utf-8") for k, v in sorted(mydict.items())}
 
 
 def _load_dict(
     langcode: str, listpath: str = "lists", silent: bool = True
-) -> Dict[str, str]:
+) -> Dict[ByteString, ByteString]:
     filepath = _determine_path(listpath, langcode)
     return _read_dict(filepath, langcode, silent)