Make some code py3 compatible

When I did `pip install pyes` I get these errors
```
Running setup.py install for pyes
      File "/usr/local/lib/python3.3/site-packages/pyes/contrib/mappings.py", line 34
        print "\n".join(res)
                 ^
    SyntaxError: invalid syntax

      File "/usr/local/lib/python3.3/site-packages/pyes/pyesthrift/simple_test.py", line 29
        print client.execute(res)
                   ^
    SyntaxError: invalid syntax

      File "/usr/local/lib/python3.3/site-packages/pyes/utils/imports.py", line 96
        raise ValueError, ValueError(
                        ^
    SyntaxError: invalid syntax
```

To the best of my knowledge the following patches should fix them. I am a bit unsure about the `raise ... from` fix. Someone should validate if that is the correct fix or not.