Fix bytes compatibility for Python 2

nd2reader/artificial.py

@@ -177,7 +177,7 @@ class ArtificialND2(object):
         elif isinstance(data, float):
             raw_data = struct.pack('d', data)
         elif isinstance(data, str):
-            raw_data = bytes(data, 'utf-8')
+            raw_data = six.b(data)
 
         return raw_data
 
@@ -198,7 +198,7 @@ class ArtificialND2(object):
 
         for data_key in data.keys():
             # names have always one character extra and are padded in zero bytes???
-            b_data_key = b''.join([struct.pack('cx', bytes(s, 'utf-8')) for s in data_key]) + struct.pack('xx')
+            b_data_key = six.b('').join([struct.pack('cx', six.b(s)) for s in data_key]) + struct.pack('xx')
 
             # header consists of data type and length of key name, it is represented by 2 unsigned chars
             raw_data += struct.pack('BB', self._get_data_type(data[data_key]), len(data_key) + 1)

tests/test_raw_metadata.py

@@ -1,4 +1,5 @@
 import unittest
+import six
 
 from nd2reader.artificial import ArtificialND2
 from nd2reader.label_map import LabelMap
@@ -39,7 +40,7 @@ class TestRawMetadata(unittest.TestCase):
 
     def _assert_dicts_equal(self, parsed_dict, original_dict):
         for attribute in original_dict.keys():
-            parsed_key = bytes(attribute, 'utf-8')
+            parsed_key = six.b(attribute)
             self.assertIn(parsed_key, parsed_dict.keys())
 
             if isinstance(parsed_dict[parsed_key], dict):