Bug 1620744 - Convert variables.py:source_repo_header() to py3; r=firefox-build-system-reviewers,rstewart

Differential Revision: https://phabricator.services.mozilla.com/D65850

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

build/variables.py

@@ -25,7 +25,8 @@ def buildid_header(output):
 def get_program_output(*command):
     try:
         with open(os.devnull) as stderr:
-            return subprocess.check_output(command, stderr=stderr)
+            return subprocess.check_output(command, stderr=stderr,
+                                           universal_newlines=True)
     except Exception:
         return ''
 

moz.build

@@ -164,7 +164,6 @@ if not CONFIG['JS_STANDALONE'] or not CONFIG['MOZ_BUILD_APP']:
 
     GENERATED_FILES['buildid.h'].script = 'build/variables.py:buildid_header'
     GENERATED_FILES['source-repo.h'].script = 'build/variables.py:source_repo_header'
-    GENERATED_FILES['source-repo.h'].py2 = True
 
     DIRS += [
         'build',