Steps to reproduce:

1) Install Courier 2.5 from Package Repository

2) Uninstall

3) Install again.

umbraco.DataLayer.SqlHelperException: Umbraco Exception (DataLayer): SQL helper exception in ExecuteNonQuery ---> MySql.Data.MySqlClient.MySqlException: Table 'ucusersettings' already exists at MySql.Data.MySqlClient.MySqlStream.OpenPacket() at MySql.Data.MySqlClient.NativeDriver.ReadResult(UInt64& affectedRows, Int64& lastInsertId) at MySql.Data.MySqlClient.MySqlDataReader.GetResultSet() at MySql.Data.MySqlClient.MySqlDataReader.NextResult() at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior) at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery() at MySql.Data.MySqlClient.MySqlHelper.ExecuteNonQuery(MySqlConnection connection, String commandText, MySqlParameter[] commandParameters) at MySql.Data.MySqlClient.MySqlHelper.ExecuteNonQuery(String connectionString, String commandText, MySqlParameter[] parms) at umbraco.DataLayer.SqlHelpers.MySql.MySqlHelper.ExecuteNonQuery(String commandText, MySqlParameter[] parameters) at umbraco.DataLayer.SqlHelper`1.ExecuteNonQuery(String commandText, IParameter[] parameters) --- End of inner exception stack trace --- at umbraco.DataLayer.SqlHelper`1.ExecuteNonQuery(String commandText, IParameter[] parameters) at Umbraco.Courier.UI.Usercontrols.Installer.Page_Load(Object sender, EventArgs e)