Convert embed datetime timestamp to iso8610 format for api calls.

disco/api/client.py

@@ -165,7 +165,7 @@ class APIClient(LoggingClass):
             payload['content'] = content
 
         if embed:
-            payload['embed'] = embed.to_dict()
+            payload['embed'] = embed.to_dict(iso=True)
 
         if attachments:
             if len(attachments) > 1:
@@ -197,7 +197,7 @@ class APIClient(LoggingClass):
             payload['content'] = content
 
         if embed:
-            payload['embed'] = embed.to_dict()
+            payload['embed'] = embed.to_dict(iso=True)
 
         r = self.http(Routes.CHANNELS_MESSAGES_MODIFY,
                       dict(channel=channel, message=message),

disco/types/message.py

@@ -4,6 +4,8 @@ import warnings
 import functools
 import unicodedata
 
+from datetime import datetime as real_datetime
+
 from disco.types.base import (
     SlottedModel, Field, ListField, AutoDictField, snowflake, text,
     datetime, enum, cached_property,
@@ -328,6 +330,14 @@ class MessageEmbed(SlottedModel):
         """
         self.fields.append(MessageEmbedField(*args, **kwargs))
 
+    def to_dict(self, iso=False):
+        data = super(MessageEmbed, self).to_dict()
+        # Ensure api calls don't try to send a non-json serializable datetime object.
+        if iso and isinstance(data.get("timestamp"), real_datetime):
+            data["timestamp"] = data["timestamp"].isoformat()
+
+        return data
+
 
 class MessageAttachment(SlottedModel):
     """