In Python how to convert an `email.message.Message` object into an `email.message.EmailMessage` object

Question

From my understanding the mbox class in Python 3.6's standard library generates old-style message objects of the type email.message.Message.

The newer class email.message.EmailMessage introduced in 3.4/3.6 offers easier access to the content of the message (via get_content() and get_body()). How can I convert the email.message.Message objects I get from the mbox iterator into email.message.EmailMessage objects?

Answer 1

Taking @ManuelJaco's comment I was able to create an mbox instance which contains automatically message objects of the type email.message.EmailMessage:

def make_EmailMessage(f):
    """Factory to create EmailMessage objects instead of Message objects"""
    return email.message_from_binary_file(f, policy=epolicy.default)

mbox = mailbox.mbox(mboxfile, factory=make_EmailMessage)

When iterating over mbox all messages (even messages contained in a message!) are of the email.message.EmailMessage type.