Serialized then deserialized Datetimes are not equal

As a new user, I would expect the following code to work correctly:

from marshmallow import Schema, fields
from datetime import datetime as dt, timezone as tz

class User():
    def __init__(self, datetime):
        self.datetime = datetime

class UserSchema(Schema):
    datetime = fields.DateTime()

user = User(dt.now())
serialized = UserSchema().dump(user).data
deserialized = UserSchema().load(serialized).data

assert user.datetime == deserialized['datetime']

Now since the DateTime field serializes differently when python-dateutil is available, there are two cases:

python-dateutil is available

The above will fail since the utc timezone is added to the serialized datetime, which was timezone unaware before serialization.

python-dateutil is not available

It will also fail in this case, since when python-dateutil is not available neither microsecond or timezone is deserialized in ISO format. They are however correctly serialized.

[sloria]

@palango I’ve cut 3.0.0rc8 that has the relevant change.

[palango]

@lafrech I just ran into that problem. Can you maybe release a new RC with these fixes?