Use in-memory cache if dummy cache is set

Author: scuml

README.md

@@ -54,7 +54,7 @@ After installation, you now need to redirect mail to the mail toolbar.  Change y
 EMAIL_BACKEND = 'mail_panel.backend.MailToolbarBackend'
 ```
 
-**Important:** This plugin uses Django's cache backend to store messages.  If you are using `DummyCache`, the mail panel will not work.  
+**Important:** This plugin uses Django's cache backend to store messages.  If you are using `DummyCache`, the mail panel will use a local memory cache, and will reset messages when the server is restarted.
 
 
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@@ -119,4 +119,4 @@ Like Django Mail Panel?  Be sure to check out and support these other tools for
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mail_panel/utils.py

@@ -1,7 +1,16 @@
-from django.core.cache import cache
+from django.core.cache import cache, caches
 
 from .conf import MAIL_TOOLBAR_CACHE_KEY, MAIL_TOOLBAR_TTL
 
+# Use local memory cache if default cache is a DummyCache
+if caches.settings.get('default', {}).get('BACKEND', '').endswith('.DummyCache'):
+    caches.settings['mail_panel'] = {
+        'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
+        'LOCATION': 'mail-panel',
+    }
+    cache = caches.create_connection('mail_panel')
+
+
 def load_outbox():
     """
     Returns a dictionary of cached mail.