gistfile1.cs

protected override IEnumerable<IValueSetCode> GetEntries(bool negation)
{
    // we currently are not importing allergies, but they should be here soon ...
    if (DateTime.Now > new DateTime(2015, 3, 1))
    {
        throw new NotSupportedException("We still have no allergies imported!");
    }
    return Enumerable.Empty<IValueSetCode>();
}

public static partial class YourNaggingTools
{
   public static void DoItBy(this string whatNeedsDone, int year, int month, int day)
   {
      if (DateTime.Now > new DateTime(year, month, day))
         throw new NotSupportedExceptions(whatNeedsToBeDone);
   }
}

Has the advantage of making the calls easy to find... use like

   "We still have no allergies imported!".DoItBy(2015, 3, 1);