Fixing async bug in Python 3.7

In python 3.7 async became a reserved word, so change it to async_.
Consider kicking out python from the project.

scripts/gen_actor_source.py

@@ -56,7 +56,7 @@ and '|' is 'or'):
     class Method :=
         name: class Name
         returnType: class BaseType | None
-        async: bool
+        async_: bool
         arguments: (class Argument)*
 
     class BaseType :=
@@ -754,9 +754,9 @@ class Method:
         else:
             self.return_type = None
         if "async" in json_node:
-            self.async = bool(json_node["async"])
+            self.async_ = bool(json_node["async"])
         else:
-            self.async = self.return_type is None
+            self.async_ = self.return_type is None
         self.arguments = []
         if "arguments" in json_node:
             for arg in json_node["arguments"]:
@@ -1966,7 +1966,7 @@ private:
             method_index = self._module.methods.index(method)
             switch_body += "case 0x%04x: {\n" % method_index
             switch_body += "    /* %s */\n" % method.name.get_ascii_value()
-            if method.async:
+            if method.async_:
                 switch_body += "    Q_EMIT asyncRun(index, args);\n"
                 switch_body += "    return ES_Async;\n"
             else:
@@ -2057,7 +2057,7 @@ private:
         for method in self._module.methods:
             assert isinstance(method, Method)
             method_index = self._module.methods.index(method)
-            if method.async:
+            if method.async_:
                 switch_body += "case 0x%04x: {\n" % method_index
                 switch_body += "    /* %s */\n" % method.name.get_ascii_value()
                 args = []
@@ -2193,7 +2193,7 @@ private:
         """
         body = "module_ = new %s(this);\n" % self._module.get_module_cpp_class_name()
         methods = self._module.methods
-        async_methods = list(filter(lambda method: method.async, methods))
+        async_methods = list(filter(lambda method: method.async_, methods))
         if self._module.settings:
             body += self._module.settings.get_settings_page_creation("settingsPage_").strip() + "\n\n"
         if async_methods:
@@ -2495,7 +2495,7 @@ class AsyncThreadCppClass(CppClassBase):
         :return:    implementation of void run()
         """
         switch_body = ""
-        methods = filter(lambda module_method: module_method.async, self._module.methods)
+        methods = filter(lambda module_method: module_method.async_, self._module.methods)
         for method in methods:
             assert isinstance(method, Method)
             method_index = self._module.methods.index(method)