Fix remaining {\rm ...} construct.

Doc/lib/libexcs.tex

@@ -169,7 +169,7 @@ Raised when an \keyword{assert} statement fails.
 \begin{excdesc}{ImportError}
 % XXXJH xref to import statement?
   Raised when an \keyword{import} statement fails to find the module
-  definition or when a \code{from {\rm \ldots} import} fails to find a
+  definition or when a \code{from \textrm{\ldots} import} fails to find a
   name that is to be imported.
 \end{excdesc}