dependencies: rm pyaes from requirements

Since #6014, pyaes is not really needed anymore.

As we currently require either one of pycryptodomex or cryptography,
even if pyaes is available, it will not be used.
We could strip it out completely from crypto.py...

In any case, pyaes is still pulled in by some hw wallet dependencies indirectly;
but the core library no longer depends on it.

electrum/crypto.py

@@ -30,12 +30,18 @@ import hashlib
 import hmac
 from typing import Union
 
-import pyaes
-
 from .util import assert_bytes, InvalidPassword, to_bytes, to_string, WalletFileException
 from .i18n import _
 
 
+HAS_PYAES = False
+try:
+    import pyaes
+except:
+    pass
+else:
+    HAS_PYAES = True
+
 HAS_CRYPTODOME = False
 try:
     from Cryptodome.Cipher import ChaCha20_Poly1305 as CD_ChaCha20_Poly1305
@@ -97,10 +103,12 @@ def aes_encrypt_with_iv(key: bytes, iv: bytes, data: bytes) -> bytes:
         cipher = CG_Cipher(CG_algorithms.AES(key), CG_modes.CBC(iv), backend=CG_default_backend())
         encryptor = cipher.encryptor()
         e = encryptor.update(data) + encryptor.finalize()
-    else:
+    elif HAS_PYAES:
         aes_cbc = pyaes.AESModeOfOperationCBC(key, iv=iv)
         aes = pyaes.Encrypter(aes_cbc, padding=pyaes.PADDING_NONE)
         e = aes.feed(data) + aes.feed()  # empty aes.feed() flushes buffer
+    else:
+        raise Exception("no AES backend found")
     return e
 
 
@@ -113,10 +121,12 @@ def aes_decrypt_with_iv(key: bytes, iv: bytes, data: bytes) -> bytes:
         cipher = CG_Cipher(CG_algorithms.AES(key), CG_modes.CBC(iv), backend=CG_default_backend())
         decryptor = cipher.decryptor()
         data = decryptor.update(data) + decryptor.finalize()
-    else:
+    elif HAS_PYAES:
         aes_cbc = pyaes.AESModeOfOperationCBC(key, iv=iv)
         aes = pyaes.Decrypter(aes_cbc, padding=pyaes.PADDING_NONE)
         data = aes.feed(data) + aes.feed()  # empty aes.feed() flushes buffer
+    else:
+        raise Exception("no AES backend found")
     try:
         return strip_PKCS7_padding(data)
     except InvalidPadding: