Make proton, gen_wrapper and user_settings python scripts version-agnostic

lsteamclient/gen_wrapper.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 
 #NOTE: If you make modifications here, consider whether they should
 #be duplicated in ../vrclient/gen_wrapper.py
@@ -502,7 +502,7 @@ for sdkver in sdk_versions:
 
         diagnostics = list(tu.diagnostics)
         if len(diagnostics) > 0:
-            print 'There were parse errors'
+            print('There were parse errors')
             pprint.pprint(diagnostics)
         else:
             children = list(tu.cursor.get_children())