Improve exception message even more

lib/Doctrine/DBAL/DBALException.php

@@ -80,7 +80,10 @@ class DBALException extends \Exception
     {
         return new self('Unknown column type "'.$name.'" requested. Any Doctrine type that you use has ' .
             'to be registered with \Doctrine\DBAL\Types\Type::addType(). You can get a list of all the ' .
-            'known types with \Doctrine\DBAL\Types\Type::getTypeMap(). If the type name is empty you might ' .
+            'known types with \Doctrine\DBAL\Types\Type::getTypeMap(). If this error occurs during database ' .
+            'introspection then you might have forgot to register all database types for a Doctrine Type. Use ' .
+            'AbstractPlatform#registerDoctrineTypeMapping() or have your custom types implement ' .
+            'Type#getMappedDatabaseTypes(). If the type name is empty you might ' .
             'have a problem with the cache or forgot some mapping information.'
         );
     }