Use in 

"in is definitely more pythonic." - http://stackoverflow.com/a/1323426
```
 line 2108, in load
  File "c:\users\jose.torres\src\pyjs\pyjs\__init__.py", line 23, in <module>
    if os.environ.has_key('PYJSPATH'):
AttributeError: '_Environ' object has no attribute 'has_key'
```
"Removed. dict.has_key() – use the in operator instead." - http://docs.python.org/3.1/whatsnew/3.0.html#builtins