AddonManager: Fix python imports

Move misplaced imports from addonmanager_macro to addonmanager_workers

src/Mod/AddonManager/addonmanager_workers.py

@@ -28,7 +28,7 @@ import stat
 import sys
 import tempfile
 
-from PySide import QtCore
+from PySide import QtCore, QtGui
 
 import FreeCAD
 if FreeCAD.GuiUp:
@@ -59,6 +59,13 @@ try:
 except ImportError:
     pass
 
+try:
+    import StringIO as io
+    _stringio = io.StringIO
+except ImportError:  # StringIO is not available with python3
+    import io
+    _stringio = io.BytesIO
+
 #  @package AddonManager_workers
 #  \ingroup ADDONMANAGER
 #  \brief Multithread workers for the addon manager