Bug 1620744 - Convert generated_sources.py to py3; r=firefox-build-system-reviewers,rstewart

Differential Revision: https://phabricator.services.mozilla.com/D65853

--HG--
extra : moz-landing-system : lando

Makefile.in

@@ -229,7 +229,7 @@ update-packaging:
 
 .PHONY: package-generated-sources
 package-generated-sources:
-	$(call py_action,package_generated_sources,'$(DIST)/$(PKG_PATH)$(GENERATED_SOURCE_FILE_PACKAGE)')
+	$(call py3_action,package_generated_sources,'$(DIST)/$(PKG_PATH)$(GENERATED_SOURCE_FILE_PACKAGE)')
 
 ifdef JS_STANDALONE
 # Delegate js-specific rules to js

python/mozbuild/mozbuild/generated_sources.py

@@ -39,7 +39,7 @@ def get_generated_sources():
 
     # First, get the list of generated sources produced by the build backend.
     gen_sources = os.path.join(buildconfig.topobjdir, 'generated-sources.json')
-    with open(gen_sources, 'rb') as f:
+    with open(gen_sources, 'r') as f:
         data = json.load(f)
     for f in data['sources']:
         yield f, mozpath.join(buildconfig.topobjdir, f)