bpo-39882: Add _Py_FatalErrorFormat() function (GH-19157)

diff --git a/Python/frozenmain.c b/Python/frozenmain.c
index 7f9cc19..508721b 100644
--- a/Python/frozenmain.c
+++ b/Python/frozenmain.c
@@ -99,7 +99,7 @@
 
     n = PyImport_ImportFrozenModule("__main__");
     if (n == 0)
-        Py_FatalError("__main__ not frozen");
+        Py_FatalError("the __main__ module is not frozen");
     if (n < 0) {
         PyErr_Print();
         sts = 1;