Make the error msgs in our pow() implementations consistent.

Objects/floatobject.c

@@ -495,8 +495,8 @@ float_pow(PyObject *v, PyObject *w, PyObject *z)
 	double iv, iw, ix;
 
 	if ((PyObject *)z != Py_None) {
-		PyErr_SetString(PyExc_TypeError,
-			"3rd argument to floating pow() must be None");
+		PyErr_SetString(PyExc_TypeError, "pow() 3rd argument not "
+			"allowed unless all other arguments are integers");
 		return NULL;
 	}
 

Objects/intobject.c

@@ -589,8 +589,8 @@ int_pow(PyIntObject *v, PyIntObject *w, PyIntObject *z)
 	CONVERT_TO_LONG(w, iw);
 	if (iw < 0) {
 		if ((PyObject *)z != Py_None) {
-			PyErr_SetString(PyExc_TypeError, "integer pow() arg "
-			     "3 must not be specified when arg 2 is < 0");
+			PyErr_SetString(PyExc_TypeError, "pow() 2nd argument "
+			     "cannot be negative when 3rd argument specified");
 			return NULL;
 		}
 		/* Return a float.  This works because we know that
@@ -603,7 +603,7 @@ int_pow(PyIntObject *v, PyIntObject *w, PyIntObject *z)
 		CONVERT_TO_LONG(z, iz);
 		if (iz == 0) {
 			PyErr_SetString(PyExc_ValueError,
-					"pow() arg 3 cannot be 0");
+					"pow() 3rd argument cannot be 0");
 			return NULL;
 		}
 	}

Objects/longobject.c

@@ -1685,15 +1685,22 @@ long_pow(PyObject *v, PyObject *w, PyObject *x)
 		Py_INCREF(Py_NotImplemented);
 		return Py_NotImplemented;
 	}
-	
+
+	if (c != Py_None && ((PyLongObject *)c)->ob_size == 0) {
+		PyErr_SetString(PyExc_ValueError,
+				"pow() 3rd argument cannot be 0");
+		z = NULL;
+		goto error;
+	}
+
 	size_b = b->ob_size;
 	if (size_b < 0) {
 		Py_DECREF(a);
 		Py_DECREF(b);
 		Py_DECREF(c);
 		if (x != Py_None) {
-			PyErr_SetString(PyExc_TypeError, "integer pow() arg "
-			     "3 must not be specified when arg 2 is < 0");
+			PyErr_SetString(PyExc_TypeError, "pow() 2nd argument "
+			     "cannot be negative when 3rd argument specified");
 			return NULL;
 		}
 		/* Return a float.  This works because we know that