Code improvement

Small code improvement  :P

```python
>>> from timeit import timeit


>>> timeit("""sys.version_info.major == 3""")
0.01277509880065918

>>> timeit("""if sys.version_info.major == 3:
...     IS_PYTHON3 = True
... else:
...     IS_PYTHON3 = False""")
0.16496182441711426
```