Add EXPERIMENTAL warning, expand text/plain hack checking.

Author: Johannes Gijsbers

roundup/backends/back_tsearch2.py

@@ -1,3 +1,5 @@
+# Note: this backend is EXPERIMENTAL. Do not use if you value your data.
+
 import re
 
 import psycopg
@@ -210,6 +212,6 @@ def __init__(self, db, classname, **properties):
     default_mime_type = 'text/plain'
     def create(self, **propvalues):
         # figure the mime type
-        if not propvalues.get('type'):
+        if 'type' in self.getprops() and not propvalues.get('type'):
             propvalues['type'] = self.default_mime_type
         return Class.create(self, **propvalues)