flake8 compliance

photobooth/gui/Qt5Gui/__init__.py

@@ -19,6 +19,6 @@
 
 # Available style sheets as tuples of (style name, style file)
 styles = (('default', 'stylesheets/default.qss'),
-		  ('dark', 'stylesheets/dark.qss'))
+          ('dark', 'stylesheets/dark.qss'))
 
 from .PyQt5Gui import PyQt5Gui  # noqa

photobooth/gui/Qt5Gui/stylesheets/dark.qss

@@ -10,6 +10,10 @@ QTabWidget {
     color: #eeeeee;
 }
 
+QTabWidget::tab-bar {
+    alignment: center;
+}
+
 QTabBar::tab {
     background-color: #333333;
     border-style: outset;