Use CharField, not TextField for MySQL compat.

todo/mail/consumers/tracker.py

@@ -97,7 +97,16 @@ def insert_message(task_list, message, priority, task_title_format):
         f"[From: {message['from']}]"
     )
 
-    message_id = message["message-id"]
+    # Due to limitations in MySQL wrt unique_together and TextField (grrr),
+    # we must use a CharField rather than TextField for message_id.
+    # In the unlikeley event that we get a VERY long inbound
+    # message_id, truncate it to the max_length of a MySQL CharField.
+    original_message_id = message["message-id"]
+    message_id = (
+        (original_message_id[:252] + "...")
+        if len(original_message_id) > 255
+        else original_message_id
+    )
     message_from = message["from"]
     text = message_text(message)
 

todo/migrations/0008_mail_tracker.py

@@ -1,4 +1,4 @@
-# Generated by Django 2.1.4 on 2018-12-21 14:01
+# Generated by Django 2.1.7 on 2019-03-24 22:50
 
 from django.conf import settings
 from django.db import migrations, models
@@ -18,7 +18,7 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name="comment",
             name="email_message_id",
-            field=models.TextField(blank=True, null=True),
+            field=models.CharField(blank=True, max_length=255, null=True),
         ),
         migrations.AlterField(
             model_name="comment",

todo/models.py

@@ -130,7 +130,7 @@ class Comment(models.Model):
     task = models.ForeignKey(Task, on_delete=models.CASCADE)
     date = models.DateTimeField(default=datetime.datetime.now)
     email_from = models.CharField(max_length=320, blank=True, null=True)
-    email_message_id = models.TextField(blank=True, null=True)
+    email_message_id = models.CharField(max_length=255, blank=True, null=True)
 
     body = models.TextField(blank=True)