MIL-003: Step 2 - New flash cards

Review record RC-025 (Go, autonomous mode, not independent).

Task: MIL-003#1
Task: MIL-003#2
Task: MIL-003#3
Task: MIL-003#4
Task: MIL-003#5

src/flash_card/domain/errors/vocabulary_errors.py

@@ -0,0 +1,21 @@
+"""Errors of the vocabulary and the deck.
+
+@file vocabulary_errors.py
+@brief The VocabularyError hierarchy.
+"""
+
+
+class VocabularyError(Exception):
+    """Base of every error about the word list or the deck."""
+
+
+class VocabularyFormatError(VocabularyError):
+    """The word list is not in the expected format."""
+
+
+class VocabularyNotFoundError(VocabularyError):
+    """The word list does not exist."""
+
+
+class EmptyDeckError(VocabularyError):
+    """A card was drawn from a deck with no card."""