Re: [PATCH] p7519: allow running without watchman prereq

I could do without the 'else' block here, but it seems straightforward
enough. Likewise, the "ensure no silent error" comment could certainly
be removed (since 'test_must_be_empty error' makes what is happening
quite clear), but the fix pursued here is minimal.

This looks great to me. Thanks for fixing - and appreciate the else
clause here for the reader.

--Nipunn