closes bpo-39630: Update pointers to string literals to be const char *. (GH-18510)

diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 4469e3c..64f5754 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -475,7 +475,7 @@
         if (new_stack.depth > current_stack.depth ||
             top_block(&new_stack)->start_line != current_block_at_new_depth->start_line) {
             unsigned char target_kind = top_block(&new_stack)->kind;
-            char *msg;
+            const char *msg;
             if (target_kind == POP_EXCEPT) {
                 msg = "can't jump into an 'except' block as there's no exception";
             }
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 0837698..ef892bb 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -12,10 +12,10 @@
 static PyObject *async_gen_asend_new(PyAsyncGenObject *, PyObject *);
 static PyObject *async_gen_athrow_new(PyAsyncGenObject *, PyObject *);
 
-static char *NON_INIT_CORO_MSG = "can't send non-None value to a "
+static const char *NON_INIT_CORO_MSG = "can't send non-None value to a "
                                  "just-started coroutine";
 
-static char *ASYNC_GEN_IGNORED_EXIT_MSG =
+static const char *ASYNC_GEN_IGNORED_EXIT_MSG =
                                  "async generator ignored GeneratorExit";
 
 static inline int
diff --git a/Python/codecs.c b/Python/codecs.c
index ce86cb2..e5bcdb0 100644
--- a/Python/codecs.c
+++ b/Python/codecs.c
@@ -1407,7 +1407,7 @@
 static int _PyCodecRegistry_Init(void)
 {
     static struct {
-        char *name;
+        const char *name;
         PyMethodDef def;
     } methods[] =
     {
diff --git a/Python/errors.c b/Python/errors.c
index f11b66e..61dc597 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -614,7 +614,7 @@
 
 #ifndef MS_WINDOWS
     if (i != 0) {
-        char *s = strerror(i);
+        const char *s = strerror(i);
         message = PyUnicode_DecodeLocale(s, "surrogateescape");
     }
     else {