Set the policy for email.message_from_*

Otherwise they default to the Compat32 policy, which isn't want we want,
since we end up with a mixture of new and old types.

Fixes: #1292

alot/commands/envelope.py

@@ -222,7 +222,8 @@ async def apply(self, ui):
         # determine account to use for sending
         msg = self.mail
         if not isinstance(msg, email.message.Message):
-            msg = email.message_from_string(self.mail)
+            msg = email.message_from_string(
+                self.mail, policy=email.policy.SMTP)
         address = msg.get('From', '')
         logging.debug("FROM: \"%s\"" % address)
         try:

alot/db/message.py

@@ -3,6 +3,7 @@
 # For further details see the COPYING file
 import email
 import email.charset as charset
+import email.policy
 import functools
 from datetime import datetime
 
@@ -103,7 +104,8 @@ def get_email(self):
                 with open(path, 'rb') as f:
                     self._email = utils.decrypted_message_from_bytes(f.read())
             except IOError:
-                self._email = email.message_from_string(warning)
+                self._email = email.message_from_string(
+                    warning, policy=email.policy.SMTP)
         return self._email
 
     def get_date(self):

alot/db/utils.py

@@ -209,7 +209,7 @@ def _handle_encrypted(original, message):
 
     if malformed:
         msg = u'Malformed OpenPGP message: {0}'.format(malformed)
-        content = email.message_from_string(msg)
+        content = email.message_from_string(msg, policy=email.policy.SMTP)
         content.set_charset('utf-8')
         original.attach(content)
 
@@ -291,7 +291,8 @@ def decrypted_message_from_bytes(bytestring):
 
     :param bytes bytestring: an email message as raw bytes
     """
-    return decrypted_message_from_message(email.message_from_bytes(bytestring))
+    return decrypted_message_from_message(
+        email.message_from_bytes(bytestring, policy=email.policy.SMTP))
 
 
 def extract_headers(mail, headers=None):