How can I detect if a schema exists?

I was reviving an old test program which hasn't been used since 9.1 and found that "SET search_path = xyzzy" no longer
failsif the schema "xyzzy" doesn't exist. 

Is there an approved or recommended way to tell if a schema exists?  I can think of lots of ways, but none as easy as
the9.1 search_path.  I suppose I shouldn't rely on undocumented features ... 

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     Felix Finch: scarecrow repairman & rocket surgeon / felix@crowfix.com
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I've found a solution to Fermat's Last Theorem but I see I've run out of room o