setting pass to an empty string, removing truncate

util/vpc-tools/sanitize-db.sql

 SET FOREIGN_KEY_CHECKS=0;
 
 /*
-  Truncate the courseware_studentmodulehistory table since
-  it is only needed for analytics    
-*/
-
-TRUNCATE courseware_studentmodulehistory;
-
-/*
   Rewrite all emails to used the SES simulator, simulating success.
   Anonymize other user information
 */
@@ -21,7 +14,7 @@ UPDATE wwc.auth_user
         where email not like ('%@edx.org'),
     set last_name = concat('user-',cast(id AS CHAR)
         where email not like ('%@edx.org'),
-    set password = null
+    set password = ""
         where email not like ('%@edx.org'),
     set last_login = null
         where email not like ('%@edx.org'),