Better error message if $SCSH_LIB_DIRS contains garbage.

scsh/lib-dirs.scm

@@ -76,8 +76,14 @@
                 (cond ((eof-object? val) '())
                       ((string? val) (cons val (recur)))
                       ((not val) (append default-lib-dirs (recur)))
-                      (else (error "Illegal path element in $SCSH_LIB_DIRS"
-                                   s val)))))))))
+                      (else 
+                       (error 
+                        (format #f
+                                (string-append
+                                 "Illegal path element in $SCSH_LIB_DIRS\n"
+                                 "$SCSH_LIB_DIRS: ~a\n"
+                                 "The following element is not a string or #f: ~a")
+                                s val))))))))))
 
 ;; We don't want to try to parse $SCSH_LIB_DIRS until we actually
 ;; need the value -- if the user is using the -lp-default switch,