is there any change that dname is not found (so that ```sample.get("barcode_name",False)``` returns False)? If so, ```os.path.join``` will crash:

```
In [3]: os.path.join('dir', False, '*.fastq')
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-3-736422da1d20> in <module>()
----> 1 os.path.join('dir', False, '*.fastq')

/Users/guillem/anaconda/envs/master/python.app/Contents/lib/python2.7/posixpath.pyc in join(a, *p)
     73     path = a
     74     for b in p:
---> 75         if b.startswith('/'):
     76             path = b
     77         elif path == '' or path.endswith('/'):

AttributeError: 'bool' object has no attribute 'startswith'
```