Index: /trunk/src/libs/xpcom18a4/python/src/ErrorUtils.cpp
===================================================================
--- /trunk/src/libs/xpcom18a4/python/src/ErrorUtils.cpp	(revision 73152)
+++ /trunk/src/libs/xpcom18a4/python/src/ErrorUtils.cpp	(revision 73153)
@@ -441,5 +441,6 @@
 	char *tempResult = PyString_AsString(obResult);
 #else
-	char *tempResult = PyUnicode_AsUTF8(obResult);
+    /* PyUnicode_AsUTF8() is const char * as of Python 3.7, char * earlier. */
+	const char *tempResult = (const char *)PyUnicode_AsUTF8(obResult);
 #endif
 	result = (char *)PyMem_Malloc(strlen(tempResult)+1);