Update imports and added PyQt4 support

combobox.py

@@ -1,7 +1,14 @@
-import sys
-from PyQt5.QtCore import *
-from PyQt5.QtGui import *
-from PyQt5.QtWidgets import *
+try:
+    from PyQt5.QtWidgets import QWidget, QHBoxLayout, QComboBox
+except ImportError:
+    # needed for py3+qt4
+    # Ref:
+    # http://pyqt.sourceforge.net/Docs/PyQt4/incompatible_apis.html
+    # http://stackoverflow.com/questions/21217399/pyqt4-qtcore-qvariant-object-instead-of-a-string
+    if sys.version_info.major >= 3:
+        import sip
+        sip.setapi('QVariant', 2)
+    from PyQt4.QtWidgets import QWidget, QHBoxLayout, QComboBox
 
 
 class ComboBox(QWidget):