BF+NF: fix missing import; raise specific errors

Raise a specific error when parsing a gifti file that does not conform
to the gifti spec.

Author: matthew-brett

nibabel/gifti/parse_gifti_fast.py

@@ -13,6 +13,7 @@
 import warnings
 import zlib
 from ..externals.six import StringIO
+from xml.parsers.expat import ExpatError
 
 import numpy as np
 
@@ -25,6 +26,10 @@
 from ..xmlutils import XmlParser
 
 
+class GiftiParseError(ExpatError):
+    """ Gifti-specific parsing error """
+
+
 def read_data_block(encoding, endian, ordering, datatype, shape, data):
     """ Tries to unzip, decode, parse the funny string data """
     ord = array_index_order_codes.npcode[ordering]
@@ -130,12 +135,12 @@ def StartElementHandler(self, name, attrs):
 
         elif name == 'Name':
             if self.nvpair is None:
-                raise ExpatError
+                raise GiftiParseError
             self.write_to = 'Name'
 
         elif name == 'Value':
             if self.nvpair is None:
-                raise ExpatError
+                raise GiftiParseError
             self.write_to = 'Value'
 
         elif name == 'LabelTable':
@@ -193,17 +198,17 @@ def StartElementHandler(self, name, attrs):
 
         elif name == 'DataSpace':
             if self.coordsys is None:
-                raise ExpatError
+                raise GiftiParseError
             self.write_to = 'DataSpace'
 
         elif name == 'TransformedSpace':
             if self.coordsys is None:
-                raise ExpatError
+                raise GiftiParseError
             self.write_to = 'TransformedSpace'
 
         elif name == 'MatrixData':
             if self.coordsys is None:
-                raise ExpatError
+                raise GiftiParseError
             self.write_to = 'MatrixData'
 
         elif name == 'Data':