Fix some style issues

Cython/Compiler/AnalysedTreeTransforms.py

 from Cython.Compiler.Visitor import VisitorTransform, ScopeTrackingTransform, TreeVisitor
-from Nodes import StatListNode, SingleAssignmentNode, CFuncDefNode
+from Nodes import StatListNode, SingleAssignmentNode, CFuncDefNode, DefNode
 from ExprNodes import DictNode, DictItemNode, NameNode, UnicodeNode, NoneNode, \
                       ExprNode, AttributeNode, ModuleRefNode, DocstringRefNode
 from PyrexTypes import py_object_type
@@ -63,9 +63,7 @@ class AutoTestDictTransform(ScopeTrackingTransform):
         return node
 
     def visit_FuncDefNode(self, node):
-        import Nodes
-        if not node.doc or (isinstance(node, Nodes.DefNode) and
-                            node.fused_py_func):
+        if not node.doc or (isinstance(node, DefNode) and node.fused_py_func):
             return node
         if not self.cdef_docstrings:
             if isinstance(node, CFuncDefNode) and not node.py_func:

Cython/Compiler/ExprNodes.py

@@ -2763,7 +2763,8 @@ class IndexNode(ExprNode):
 
                     break
             else:
-                assert False
+                # This is a bug
+                raise InternalError("Couldn't find the right signature")
 
     gil_message = "Indexing Python object"
 

Cython/Utils.py

@@ -234,4 +234,4 @@ except NameError:
         for item in items:
             if item:
                 return True
-        return False
\ No newline at end of file
+        return False