Issue #12434: make StringIO.write error message consistent with Python 2.7 nomenclature
diff --git a/Modules/_io/stringio.c b/Modules/_io/stringio.c
index cf0f8b1..e3de751 100644
--- a/Modules/_io/stringio.c
+++ b/Modules/_io/stringio.c
@@ -464,7 +464,7 @@
 
     CHECK_INITIALIZED(self);
     if (!PyUnicode_Check(obj)) {
-        PyErr_Format(PyExc_TypeError, "string argument expected, got '%s'",
+        PyErr_Format(PyExc_TypeError, "unicode argument expected, got '%s'",
                      Py_TYPE(obj)->tp_name);
         return NULL;
     }