drop unused import

Cython/Compiler/TreeFragment.py

@@ -5,7 +5,7 @@
 import re
 from StringIO import StringIO
 from Scanning import PyrexScanner, StringSourceDescriptor
-from Symtab import BuiltinScope, ModuleScope
+from Symtab import ModuleScope
 import Symtab
 import PyrexTypes
 from Visitor import VisitorTransform