On Tue, Sep 2, 2014 at 11:30 AM, Mittelbach, Frank
<[log in to unmask]> wrote:

>> Even an error message that explains the situation would be preferable
>> to the standard "File `l3prop.sty' not found" error.
> ok that's probably better than a warning. Error  and explaining what to
> change, followed by loading expl3 so that the document can continue

That seems sensible. Users have probably (and justifiably) become
desensitized to console-warnings.