Add ustr.py, add more test, and fix build error for py3

tests/test.py

@@ -1,8 +1,12 @@
+import _init_path
 
 from unittest import TestCase
 
 from labelImg import get_main_app
 
+from pascal_voc_io import PascalVocWriter
+from pascal_voc_io import PascalVocReader
+
 
 class TestMainWindow(TestCase):
 
@@ -18,3 +22,13 @@ class TestMainWindow(TestCase):
 
     def test_noop(self):
         pass
+
+# Test Write/Read
+writer = PascalVocWriter('tests', 'test', (512, 512, 1), localImgPath='tests/test.bmp')
+difficult = 1
+writer.addBndBox(60, 40, 430, 504, 'person', difficult)
+writer.addBndBox(113, 40, 450, 403, 'face', difficult)
+writer.save('tests/test.xml')
+
+reader = PascalVocReader('tests/test.xml')
+shapes = reader.getShapes()