Remove to_native/to_unicode calls from message, signers, utils

These were Python 2 compatibility helpers. On Python 3:
- to_native(s) where s is str → noop, removed
- to_native(s) where s is bytes → replaced with s.decode()
- to_unicode(s) where s is str → noop, removed
- to_unicode(value) for non-str → replaced with explicit
  bytes.decode() / str() branching

Functions kept in utils.py for now (still used by loader/).

Author: lavr

emails/message.py

@@ -6,7 +6,7 @@
 from email.utils import getaddresses
 from typing import Any, IO
 
-from .utils import (formataddr, to_unicode, to_native,
+from .utils import (formataddr,
                     SafeMIMEText, SafeMIMEMultipart, sanitize_address,
                     parse_name_and_email, load_email_charsets,
                     encode_header as encode_header_,
@@ -231,7 +231,7 @@ def set_header(self, msg: SafeMIMEMultipart, key: str,
             return
 
         if not isinstance(value, str):
-            value = to_unicode(value)
+            value = value.decode() if isinstance(value, bytes) else str(value)
 
         # Prevent header injection
         if '\n' in value or '\r' in value:
@@ -345,7 +345,7 @@ def as_string(self, message_cls: type | None = None) -> str:
         Note: this method costs one less message-to-string conversions
         for dkim in compare to self.as_message().as_string()
         """
-        r = to_native(self.build_message(message_cls=message_cls).as_string())
+        r = self.build_message(message_cls=message_cls).as_string()
         if self._signer:
             r = self.sign_string(r)
         return r

emails/signers.py

@@ -9,7 +9,7 @@
 from .packages import dkim
 from .packages.dkim import DKIMException, UnparsableKeyError
 from .packages.dkim.crypto import parse_pem_private_key
-from .utils import to_bytes, to_native
+from .utils import to_bytes
 
 
 class DKIMSigner:
@@ -61,9 +61,7 @@ def get_sign_header(self, message: bytes) -> tuple[str, str] | None:
         # pydkim returns string, so we should split
         s = self.get_sign_string(message)
         if s:
-            native = to_native(s)
-            assert native is not None  # s is bytes, to_native always returns str
-            (header, value) = native.split(': ', 1)
+            (header, value) = s.decode().split(': ', 1)
             if value.endswith("\r\n"):
                 value = value[:-2]
             return header, value
@@ -98,9 +96,7 @@ def sign_message_string(self, message_string: str) -> str:
         assert msg_bytes is not None
         s = self.get_sign_string(msg_bytes)
         if s:
-            header = to_native(s)
-            assert header is not None
-            return header + message_string
+            return s.decode() + message_string
         return message_string
 
     def sign_message_bytes(self, message_bytes: bytes) -> bytes:

emails/utils.py

@@ -219,7 +219,7 @@ def parse_name_and_email(obj: str | tuple[str | None, str] | list[str],
     else:
         raise ValueError("Can not parse_name_and_email from %s" % obj)
 
-    return to_unicode(name, encoding) or None, to_unicode(email, encoding) or None
+    return name or None, email or None
 
 
 def sanitize_email(addr: str, encoding: str = 'ascii', parse: bool = False) -> str: