make test more "hermetic"

Author: MichaelChirico

inst/tests/tests.Rraw

@@ -20800,7 +20800,8 @@ baz(x)
 test(2295.7, is.data.table(x))
 
 # #6588: .checkTypos used to give arbitrary strings to stopf as the first argument
-test(2296, d2[x %no such operator% 1], error = '%no such operator%')
+DT = data.table(a = 1)
+test(2296, DT[x %no such operator% 1], error = '%no such operator%')
 
 # fix coercing integer/double for joins on multiple columns, #6602
 x = data.table(a=1L)