Fix #12759 (#14967)

* add testcase for #5926

* fix #12759

lib/pure/terminal.nim

@@ -37,7 +37,7 @@ type
 
 var gTerm {.threadvar.}: owned(PTerminal)
 
-proc newTerminal(): owned(PTerminal) {.gcsafe.}
+proc newTerminal(): owned(PTerminal) {.gcsafe, raises: [].}
 
 proc getTerminal(): PTerminal {.inline.} =
   if isNil(gTerm):

tests/stdlib/tterminal_12759.nim

@@ -0,0 +1,10 @@
+discard """
+  action: "compile"
+"""
+
+import terminal
+
+proc test() {.raises:[IOError, ValueError].} =
+  setBackgroundColor(stdout, bgRed)
+
+test()