fix: assign result of .upper() in _next_letter and remove unused imports

pyenigma/machine.py

@@ -50,7 +50,7 @@ def _encipher_letter(self, letter: str) -> str:
 
     @staticmethod
     def _next_letter(letter: str) -> str:
-        letter.upper()
+        letter = letter.upper()
         if letter == 'Z':
             return 'A'
         else:

pyenigma/reflector.py

@@ -1,5 +1,4 @@
 import logging
-import re
 from pyenigma.constants import ALPHABET, REFLECTOR_WIRING
 from pyenigma.exceptions import (
     ReflectorWiringWrongLengthException,

pyenigma/rotor.py

@@ -1,5 +1,4 @@
 import logging
-from math import e
 from pyenigma.constants import ALPHABET, ROTOR_WIRING, ROTOR_NOTCHES
 from pyenigma.exceptions import (
     RotorWiringWrongLengthException,

pyproject.toml

@@ -18,6 +18,7 @@ dev = [
     "pytest>=8.0",
     "mypy>=1.0",
     "coverage>=7.0",
+    "hypothesis>=6.141.1",
 ]
 
 [tool.hatch.version]