Bug 1542963 - flake8 python/mozbuild/mozbuild r=glandium

Lint python/mozbuild/{mozbuild,mozpack}.

Differential Revision: https://phabricator.services.mozilla.com/D26639

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

.flake8

@@ -25,7 +25,6 @@ exclude =
     python/devtools/migrate-l10n/migrate/main.py,
     python/l10n/fluent_migrations,
     python/mozbuild/dumbmake,
-    python/mozbuild/mozbuild,
     servo/components/style,
     testing/jsshell/benchmark.py,
     testing/marionette/mach_commands.py,
@@ -69,6 +68,7 @@ exclude =
     memory/moz.configure,
     mobile/android/*.configure,
     node_modules,
+    python/mozbuild/mozbuild/test/configure/data,
     security/nss/,
     testing/marionette/harness/marionette_harness/runner/mixins,
     testing/marionette/harness/marionette_harness/tests,