 'basestring' is not defined

Whatever I do I get the following error. I replaced `basestring` with `str` locally and get it work. 

``` python
File "/usr/local/lib/python3.4/dist-packages/ogrtools/pyogr/ogr2ogr.py", line 644, in ogr2ogr
    if isinstance(pszDataSource, basestring):
NameError: name 'basestring' is not defined
```

What is the meaning of `basestring`. Will I have a problem replacing it with `str`?
